<Page>
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM N-CSR
CERTIFIED SHAREHOLDER REPORT OF REGISTERED
MANAGEMENT INVESTMENT COMPANIES
Investment Company Act file number: 811-4919
UBS SERIES TRUST
- --------------------------------------------------------------------------------
(Exact name of registrant as specified in charter)
51 West 52nd Street, New York, New York 10019-6114
- --------------------------------------------------------------------------------
(Address of principal executive offices) (Zip code)
Amy R. Doberman
UBS Global Asset Management (US)
Inc.
51 West 52nd Street
New York, NY 10019-6114
(Name and address of agent for
service)
Copy to:
Jack W. Murphy, Esq.
Dechert
1775 I Street, N.W.
Washington, DC 20006-2401
Registrant's telephone number, including area code: 212-882 5000
Date of fiscal year end: December 31, 2003
Date of reporting period: June 30, 2003
<Page>
ITEM 1. REPORTS TO STOCKHOLDERS.
<Page>
[UBS GLOBAL ASSET MANAGEMENT LOGO]
UBS SERIES TRUST
TACTICAL ALLOCATION PORTFOLIO
SEMIANNUAL REPORT
JUNE 30, 2003
<Page>
UBS SERIES TRUST -- TACTICAL ALLOCATION PORTFOLIO
August 15, 2003
DEAR CONTRACT OWNER,
We present you with the semiannual report for UBS Series Trust--Tactical
Allocation Portfolio for the six months ended June 30, 2003.
AN INTERVIEW WITH PORTFOLIO MANAGER T. KIRKHAM BARNEBY
Q. HOW DID THE PORTFOLIO PERFORM OVER THE SIX MONTHS ENDED JUNE 30, 2003?
A. Following a prolonged market decline, the equity markets rallied, resulting
in an 11.76% gain for the S&P 500 Index over the six months ended June 30,
2003. Over the same period, the Portfolio's Class H shares returned 11.34%,
as the Tactical Allocation Model dictated a 100% allocation to equities
throughout the period (see "How the Portfolio Works" on the next page). (For
returns over various time periods, please refer to "Performance At A Glance"
on page 5.)
Q. HOW DID THE EQUITY MARKETS PERFORM DURING THE REPORTING PERIOD?
A. It was really a tale of two markets. During the first quarter of 2003, the
S&P 500 Index fell 3.15%. Economic and geopolitical uncertainties weighed
heavily on the market, so investors shunned stocks in favor of the relative
security offered by bonds. Conversely, during the second half of the review
period, the equity markets rallied sharply. The end to major fighting in Iraq
eliminated one of the larger geopolitical issues affecting the stock market,
while investors became increasingly optimistic about the potential for an
economic revival and subsequent upturn in corporate profits. At the same
time, their appetite for risk increased as the yields available from many
fixed income securities shrank. As a result, equity investors drove the S&P
500 Index to a 15.39% gain over the second quarter. The market's gains were
broad-based, and many of the best performing sectors were the prior years'
weakest-performing areas: the utility, information technology,
telecommunication services and industrial sectors.
[SIDENOTE]
UBS SERIES TRUST -- TACTICAL ALLOCATION PORTFOLIO
INVESTMENT GOAL:
Total return, consisting of long-term capital appreciation and current income.
PORTFOLIO MANAGER:
T. Kirkham Barneby,
UBS Global Asset
Management (US) Inc.
COMMENCEMENT:
Class H--September 28, 1998
Class I--January 5, 1999
DIVIDEND PAYMENTS:
Annually
1
<Page>
Q. AGAINST THIS BACKDROP, HOW WAS THE PORTFOLIO ALLOCATED DURING THE PERIOD?
A. The Portfolio maintained a 100% allocation to equities throughout the
reporting period. During the first half of the review period, this allocation
led the Portfolio's performance to decline along with the overall equity
market. However, it was beneficial to Portfolio performance when stocks
rallied in the second half of the period.
Q. WHAT WERE THE FACTORS THAT DROVE A 100% ALLOCATION TO EQUITIES?
A. As always, we adjust the Portfolio's exposure to stocks based on indications
generated by our proprietary Tactical Allocation Model. This Model measures
the attractiveness of stocks by calculating the Equity Risk Premium (ERP), an
unemotional, quantitative tool, to determine whether investors are being
adequately compensated for the risk of owning stocks.
To calculate the ERP, the Model evaluates current equity prices and future
earnings and dividend growth for the stock market versus the yield of a
one-year Constant Maturity Treasury (the riskless return over a one-year
holding period). Historically, an ERP over 5% has indicated an environment in
which stock prices have tended to rise. An ERP greater than 5.5% dictates a
100% allocation to equities. Throughout the period, the ERP remained above
10%--a high level that, according to the Model, indicates a significantly
oversold stock market.
Q. WHAT IS YOUR OUTLOOK FOR THE MARKET AND THE PORTFOLIO?
A. As of July 1, 2003, the Model's Equity Risk Premium (ERP) was 10.02%, and the
strategy continued to be fully invested in the equity market. The current ERP
reading suggests that the market continues to be significantly oversold and
presents a compelling buying opportunity for long-term investors. Past
precedent would lead us to believe this is the case as well. The behavior of
the
[SIDENOTE]
HOW THE PORTFOLIO WORKS
The Portfolio attempts to provide total return over the long term, with less
volatility than the S&P 500 Index (the "Index") over the course of a full market
cycle, by shifting assets between stocks and bonds or cash based on the Tactical
Allocation Model (the "Model"). We use the Model to determine the Portfolio's
exposure to an equity portion designed to track the performance of the Index and
a fixed-income portion consisting of either bonds (generally five-year U.S.
Treasury notes) or cash (generally 30-day U.S. Treasury bills). The Portfolio
moves away from stocks and into bonds when the Model signals a potential stock
market downturn. It moves into stocks when the Model anticipates the potential
for stock market appreciation.
2
<Page>
economy has historically been one of the basic determinants of stock market
performance. Economic indicators currently suggest that the economy is
growing, albeit at a modest pace, which, along with accomodative Federal
Reserve Policy and a low and stable inflationary environment, may provide an
environment which, in the past, has been associated with strong equity market
performance.
Past market behavior following significant declines provides additional
support for higher equity prices over the near term. The market has generally
recovered vigorously following plunges--and, oftentimes, the greater or more
prolonged decline results in a more pronounced "snap-back." The domination of
fear over investor psychology in 2002 clearly produced a plunge (the S&P 500
Index declined 22% over the 12 months ended December 31, 2002). Consequently,
we believe that as investor psychology continues to improve, a reversal of
this emotion-driven selloff could well produce higher equity prices. (Of
course, past market behavior does not guarantee a similar recovery or
performance in the future.)
The wrinkle in this positive scenario comes from, of course, the possibility
that the US economy could fall back into a recession. While this seems
unlikely given the causes of past "double-dips," such a negative scenario
cannot be ruled out entirely. More recently, Federal Reserve Chairman Alan
Greenspan cited deflation as a concern (although attaching a relatively low
probability to such an outcome). However, barring this possibility, the Fed's
forecast of growth with modest inflation--which is also reflective of many
economists' opinions--should provide a positive backdrop for the US equity
market.
Q. DO YOU ANTICIPATE THAT THE PORTFOLIO'S ASSET ALLOCATION WILL CHANGE OVER THE
NEXT FEW MONTHS?
A. As always, we'll continue to proactively monitor the factors that drive the
stock market. If the Model indicates that adjustments to the Fund's asset
allocation strategy are appropriate, those changes will be instituted. Based
on today's market environment, both stock prices and interest rates would
have to rise dramatically from their current levels in order for the Model to
indicate an allocation shift to bonds. We would generally expect to see this
combination of events occur during a more pronounced economic recovery.
3
<Page>
Our ultimate objective in managing your investments is to help you successfully
meet your financial goals. We thank you for your continued support and welcome
any comments or questions you may have. For more information on UBS funds,*
please contact your financial advisor, or visit us at www.ubs.com.
Sincerely,
/s/ Joseph A. Varnas
JOSEPH A. VARNAS
PRESIDENT
UBS Series Trust--Tactical Allocation Portfolio
MANAGING DIRECTOR
UBS Global Asset Management (US) Inc.
/s/ T. Kirkham Barneby
T. KIRKHAM BARNEBY
PORTFOLIO MANAGER
UBS Series Trust--Tactical Allocation Portfolio
MANAGING DIRECTOR
UBS Global Asset Management (US) Inc.
As with any investment discipline, there can be no guarantee that the Model will
accurately anticipate significant shifts in the markets and correctly determine
the right time to invest in stocks, bonds or cash.
This letter is intended to assist shareholders in understanding how the
Portfolio performed during the six-month period ended June 30, 2003, and
reflects our views at the time of its writing. Of course, these views may change
in response to changing circumstances, and they do not guarantee the future
performance of the markets or the Portfolio. We encourage you to consult your
financial advisor regarding your personal investment program.
*Mutual funds are sold by prospectus only. The prospectus for the Portfolio
contains more complete information regarding risks, charges and expenses and
should be read carefully before investing.
4
<Page>
PERFORMANCE AT A GLANCE
AVERAGE ANNUAL TOTAL RETURNS FOR PERIODS ENDED 6/30/03
<Table>
<Caption>
6 MONTHS 1 YEAR 3 YEARS INCEPTION^
- --------------------------------------------------------------------------
Class H 11.34% -0.47% -9.75% 1.94%
Class I 11.19 -0.84 -9.99 -3.09
S&P 500 Index 11.76 0.26 -11.20 -0.15
==========================================================================
</Table>
^ Inception: since commencement of issuance on September 28, 1998 for Class H
shares and January 5, 1999 for Class I shares. Index performance is shown as
of the inception of oldest share class: September 28, 1998.
The investment return and the principal value of an investment will fluctuate,
so that an investor's shares, when redeemed, may be worth more or less than
their original cost. Returns for periods of less than one year are not
annualized. Past performance is no guarantee of future performance. Figures
assume reinvestment of all dividends and capital gains distributions, if any, at
net asset value on the ex-dividend dates. Performance relates to the Portfolio
and does not reflect separate account charges applicable to variable annuity
contracts.
PORTFOLIO STATISTICS
<Table>
<Caption>
CHARACTERISTICS* 6/30/03 12/31/02 6/30/02
- -----------------------------------------------------------------------------------------------------------------
Equities 100.0% 100.0% 100.1%
Cash Equivalents and Other
Assets Less Liabilities -- -- (0.1)%
Number of Holdings 466 472 467
Equity Risk
Premium (ERP)** 10.02% 10.21% 9.48%
Bond Risk
Premium (BRP)** 1.31% 1.34% 2.09%
===============================================================================================================
<Caption>
TOP 5 SECTORS* 6/30/03 12/31/02 6/30/02
- -----------------------------------------------------------------------------------------------------------------
Financials 20.4% Financials 20.6% Financials 19.8%
Information Technology 15.2 Information Technology 14.3 Information Technology 13.9
Health Care 14.8 Health Care 14.9 Health Care 13.7
Consumer Discretionary 13.8 Consumer Discretionary 13.4 Consumer Discretionary 13.7
Industrials 11.5 Industrials 11.7 Industrials 11.0
- ---------------------------------------------------------------------------------------------------------------
TOTAL 75.7% 74.9% 72.1%
===============================================================================================================
<Caption>
TOP 10 HOLDINGS* 6/30/03 12/31/02 6/30/02
- -----------------------------------------------------------------------------------------------------------------
General Electric 3.2% Microsoft 3.4% Microsoft 3.3%
Microsoft 3.1 General Electric 3.0 General Electric 3.2
Pfizer 3.0 Exxon Mobil 2.9 Exxon Mobil 3.1
Exxon Mobil 2.7 Wal-Mart Stores 2.7 Wal-Mart Stores 2.7
Wal-Mart Stores 2.6 Pfizer 2.3 Pfizer 2.4
Citigroup 2.4 Citigroup 2.2 Citigroup 2.2
American International
Johnson & Johnson 1.7 Johnson & Johnson 2.0 Group 2.0
American American
International Group 1.6 International Group 1.9 Johnson & Johnson 1.7
IBM 1.6 IBM 1.6 Coca-Cola 1.5
Merck 1.5 Merck 1.6 IBM 1.4
- ---------------------------------------------------------------------------------------------------------------
TOTAL 23.4% 23.6% 23.5%
===============================================================================================================
</Table>
* Weightings represent percentages of net assets as of the dates indicated.
Portfolio weightings reflect the weightings of the S&P 500 Index and will
vary over time. The Portfolio's asset allocation is actively managed
according to the Model and will vary over time.
** The Tactical Allocation Model is run on the first business day of each month.
The ERP and BRP percentages in the 6/30/03 column are the numbers that were
run on 7/1/03; the ERP and BRP percentages in the 12/31/02 column are the
numbers that were run on 1/2/03; the ERP and BRP percentages in the 6/30/02
column are the numbers that were run on 7/1/02.
5
<Page>
Portfolio of Investments -- June 30, 2003 (unaudited)
COMMON STOCKS--99.97%
<Table>
<Caption>
SECURITY DESCRIPTION SHARES VALUE
- -------------------------------------------------------------------------------
AEROSPACE & DEFENSE--1.76%
Boeing Co. 6,700 $ 229,944
General Dynamics Corp. 1,600 116,000
Goodrich Corp. 1,000 21,000
Honeywell International, Inc. 6,800 182,580
Lockheed Martin Corp. 3,600 171,252
Northrop Grumman Corp. 1,500 129,435
Raytheon Co. 3,300 108,372
Rockwell Collins, Inc. 1,500 36,945
United Technologies Corp. 3,700 262,071
- -------------------------------------------------------------------------------
1,257,599
===============================================================================
AIR FREIGHT & COURIERS--1.01%
FedEx Corp. 2,400 148,872
United Parcel Service, Inc.,
Class B 9,000 573,300
- -------------------------------------------------------------------------------
722,172
===============================================================================
AIRLINES--0.17%
Delta Air Lines, Inc. 1,100 16,148
Southwest Airlines Co. 6,100 104,920
- -------------------------------------------------------------------------------
121,068
===============================================================================
AUTO COMPONENTS--0.18%
Dana Corp. 1,500 17,340
Delphi Automotive
Systems Corp. 4,800 41,424
Goodyear Tire &
Rubber Co.* 1,700 8,925
Johnson Controls, Inc. 700 59,920
- -------------------------------------------------------------------------------
127,609
===============================================================================
AUTOMOBILES--0.45%
Ford Motor Co. 14,700 161,553
General Motors Corp. 4,500 162,000
- -------------------------------------------------------------------------------
323,553
===============================================================================
BANKS--7.35%
AmSouth Bancorp 2,800 61,152
Bank of America Corp. 11,800 932,554
Bank of New York Co., Inc. 6,100 175,375
Bank One Corp. 9,000 334,620
BB&T Corp. 3,700 126,910
Charter One Financial, Inc. 1,900 $ 59,242
Comerica, Inc. 1,400 65,100
Fifth Third Bancorp 4,500 258,030
First Tennessee National Corp. 1,000 43,910
FleetBoston Financial Corp. 8,300 246,593
Golden West Financial Corp. 1,200 96,012
Huntington Bancshares, Inc. 2,000 39,040
KeyCorp 3,500 88,445
Marshall & Ilsley Corp. 1,900 58,102
Mellon Financial Corp. 3,500 97,125
National City Corp. 4,900 160,279
North Fork Bancorp, Inc. 1,300 44,278
Northern Trust Corp. 1,800 75,222
PNC Financial Services Group 2,300 112,263
Regions Financial Corp. 1,800 60,804
SouthTrust Corp. 2,700 73,440
SunTrust Banks, Inc. 2,200 130,548
Synovus Financial Corp. 2,500 53,750
U.S. Bancorp, Inc. 15,200 372,400
Union Planters Corp. 1,700 52,751
Wachovia Corp. 10,600 423,576
Washington Mutual, Inc. 7,300 301,490
Wells Fargo & Co. 13,200 665,280
Zions Bancorp 800 40,488
- -------------------------------------------------------------------------------
5,248,779
===============================================================================
BEVERAGES--2.79%
Anheuser-Busch Cos., Inc. 6,600 336,930
Brown-Forman Corp., Class B 500 39,310
Coca-Cola Co. 19,500 904,995
Coca-Cola Enterprises, Inc. 3,600 65,340
Pepsi Bottling Group, Inc. 2,200 44,044
PepsiCo, Inc. 13,600 605,200
- -------------------------------------------------------------------------------
1,995,819
===============================================================================
</Table>
6
<Page>
<Table>
<Caption>
SECURITY DESCRIPTION SHARES VALUE
- -------------------------------------------------------------------------------
BIOTECHNOLOGY--1.29%
Amgen, Inc.* 10,000 $ 664,400
Biogen, Inc.* 1,200 45,600
Chiron Corp.* 1,500 65,580
Genzyme Corp.* 1,700 71,060
Medimmune, Inc.* 2,000 72,740
- -------------------------------------------------------------------------------
919,380
===============================================================================
BUILDING PRODUCTS--0.19%
American Standard Cos., Inc.* 600 44,358
Masco Corp. 3,800 90,630
- -------------------------------------------------------------------------------
134,988
===============================================================================
CHEMICALS--1.48%
Air Products & Chemicals, Inc. 1,900 79,040
Dow Chemical Co. 7,300 226,008
Eastman Chemical Co. 800 25,336
Ecolab, Inc. 2,200 56,320
E.I. du Pont de Nemours & Co. 8,000 333,120
Engelhard Corp. 1,100 27,247
International Flavors &
Fragrances, Inc. 800 25,544
Monsanto Co. 2,200 47,608
PPG Industries, Inc. 1,400 71,036
Praxair, Inc. 1,300 78,130
Rohm & Haas Co. 1,800 55,854
Sigma-Aldrich Corp. 600 32,508
- -------------------------------------------------------------------------------
1,057,751
===============================================================================
COMMERCIAL SERVICES & SUPPLIES--1.89%
Allied Waste Industries, Inc.* 1,800 18,090
Apollo Group, Inc., Class A* 1,400 86,464
Automatic Data Processing, Inc. 4,700 159,142
Avery Dennison Corp. 900 45,180
Cendant Corp.* 8,100 148,392
Cintas Corp. 1,400 49,616
Concord EFS, Inc.* 3,900 57,408
Convergys Corp.* 1,200 19,200
Donnelley, R. R. & Sons Co. 1,100 $ 28,754
Equifax, Inc. 1,200 31,200
First Data Corp. 5,900 244,496
Fiserv, Inc.* 1,500 53,415
H&R Block, Inc. 1,400 60,550
Monster Worldwide, Inc.* 900 17,757
Paychex, Inc. 3,000 87,930
Pitney Bowes, Inc. 1,900 72,979
Robert Half International, Inc.* 1,500 28,410
Sabre Holdings Corp.* 1,200 29,580
Waste Management, Inc. 4,700 113,223
- -------------------------------------------------------------------------------
1,351,786
===============================================================================
COMMUNICATIONS EQUIPMENT--2.30%
ADC Telecommunications, Inc.* 6,700 15,598
Avaya, Inc.* 3,100 20,026
CIENA Corp.* 3,900 20,241
Cisco Systems, Inc.* 55,700 929,633
Comverse Technology, Inc.* 1,500 22,545
Corning, Inc.* 10,100 74,639
JDS Uniphase Corp.* 11,500 40,365
Lucent Technologies, Inc.* 33,100 67,193
Motorola, Inc. 18,500 174,455
Qualcomm, Inc. 6,300 225,225
Scientific-Atlanta, Inc. 1,200 28,608
Tellabs, Inc.* 3,400 22,338
- -------------------------------------------------------------------------------
1,640,866
===============================================================================
COMPUTERS & PERIPHERALS--3.92%
Apple Computer, Inc.* 3,000 57,360
Dell Computer Corp.* 20,400 651,984
EMC Corp.* 17,400 182,178
Gateway, Inc.* 2,900 10,585
Hewlett-Packard Co. 24,200 515,460
International Business
Machines Corp. 13,700 1,130,250
Lexmark International Group, Inc.* 1,000 70,770
</Table>
7
<Page>
<Table>
<Caption>
SECURITY DESCRIPTION SHARES VALUE
- -------------------------------------------------------------------------------
COMPUTERS & PERIPHERALS--(CONCLUDED)
NCR Corp.* 800 $ 20,496
Network Appliance, Inc.* 2,700 43,767
Sun Microsystems, Inc.* 25,700 118,220
- -------------------------------------------------------------------------------
2,801,070
===============================================================================
CONSTRUCTION & ENGINEERING--0.03%
Fluor Corp. 700 23,548
===============================================================================
CONSTRUCTION MATERIALS--0.05%
Vulcan Materials Co. 900 33,363
===============================================================================
CONTAINERS & PACKAGING--0.15%
Ball Corp. 500 22,755
Pactiv Corp.* 1,400 27,594
Sealed Air Corp.* 700 33,362
Temple-Inland, Inc. 500 21,455
- -------------------------------------------------------------------------------
105,166
===============================================================================
DIVERSIFIED FINANCIALS--8.12%
American Express Co. 10,300 430,643
Bear Stearns Co., Inc. 800 57,936
Capital One Financial Corp. 1,800 88,524
Charles Schwab Corp. 10,700 107,963
Citigroup, Inc. 40,700 1,741,960
Countrywide Credit Industries, Inc. 1,000 69,570
Federal Home Loan Mortgage Corp. 5,500 279,235
Federal National Mortgage Association 7,800 526,032
Federated Investors, Inc.,
Class B 900 24,678
Franklin Resources, Inc. 2,000 78,140
Goldman Sachs Group, Inc. 3,700 309,875
J.P. Morgan Chase & Co. 16,100 550,298
Janus Capital Group, Inc. 2,000 32,800
Lehman Brothers Holdings, Inc. 1,900 126,312
MBNA Corp. 10,100 210,484
Merrill Lynch & Co., Inc. 7,400 345,432
Moody's Corp. 1,200 63,252
Morgan Stanley & Co. 8,600 367,650
Principal Financial Group, Inc. 2,600 $ 83,850
Providian Financial Corp.* 2,400 22,224
SLM Corp. 3,600 141,012
State Street Corp. 2,700 106,380
T. Rowe Price Group, Inc. 1,000 37,750
- -------------------------------------------------------------------------------
5,802,000
===============================================================================
DIVERSIFIED TELECOMMUNICATION
SERVICES--3.36%
ALLTEL Corp.(1) 2,500 120,550
AT&T Corp. 6,300 121,275
BellSouth Corp. 14,600 388,798
CenturyTel, Inc. 1,200 41,820
Citizens Communications Co.* 2,400 30,936
Qwest Communications
International, Inc.* 13,700 65,486
SBC Communications, Inc. 26,300 671,965
Sprint Corp. (PCS Group) 7,100 102,240
Verizon Communications 21,800 860,010
- -------------------------------------------------------------------------------
2,403,080
===============================================================================
ELECTRIC UTILITIES--2.32%
Ameren Corp. 1,300 57,330
American Electric Power Co., Inc. 3,200 95,456
Cinergy Corp. 1,500 55,185
Consolidated Edison, Inc. 1,800 77,904
Constellation Energy Group, Inc. 1,400 48,020
Dominion Resources, Inc. 2,500 160,675
DTE Energy Co. 1,400 54,096
Edison International, Inc.* 2,700 44,361
Entergy Corp. 1,800 95,004
Exelon Corp. 2,600 155,506
FirstEnergy Corp. 2,400 92,280
FPL Group, Inc. 1,500 100,275
PG&E Corp.* 3,300 69,795
Pinnacle West Capital Corp. 800 29,960
PPL Corp. 1,400 60,200
</Table>
8
<Page>
<Table>
<Caption>
SECURITY DESCRIPTION SHARES VALUE
- -------------------------------------------------------------------------------
ELECTRIC UTILITIES--(CONCLUDED)
Progress Energy, Inc.*(2) 2,400 $ 83,410
Public Service
Enterprise Group, Inc. 1,800 76,050
Southern Co. 5,700 177,612
TECO Energy, Inc.(1) 1,600 19,184
TXU Corp. 2,600 58,370
Xcel Energy, Inc. 3,300 49,632
- -------------------------------------------------------------------------------
1,660,305
===============================================================================
ELECTRICAL EQUIPMENT--0.44%
American Power Conversion Corp. 1,600 24,944
Cooper Industries Ltd., Class A 800 33,040
Emerson Electric Co. 3,400 173,740
Molex, Inc. 1,600 43,184
Rockwell Automation, Inc. 1,600 38,144
- -------------------------------------------------------------------------------
313,052
===============================================================================
ELECTRONIC EQUIPMENT &
INSTRUMENTS--0.41%
Agilent Technologies, Inc.* 3,800 74,290
Jabil Circuit, Inc.* 1,600 35,360
Millipore Corp. 400 17,748
PerkinElmer, Inc. 1,100 15,191
Sanmina-SCI Corp.* 4,200 26,502
Solectron Corp.* 6,800 25,432
Symbol Technologies, Inc. 1,900 24,719
Tektronix, Inc. 700 15,120
Thermo Electron Corp.* 1,400 29,428
Waters Corp.* 1,000 29,130
- -------------------------------------------------------------------------------
292,920
===============================================================================
ENERGY EQUIPMENT & SERVICES--0.82%
Baker Hughes, Inc. 2,800 93,996
BJ Services Co.* 1,300 48,568
Halliburton Co. 3,500 80,500
Nabors Industries Ltd.* 1,200 47,460
Noble Corp.* 1,100 37,730
Schlumberger Ltd. 4,700 223,579
Transocean Sedco Forex, Inc. 2,600 57,122
- -------------------------------------------------------------------------------
588,955
===============================================================================
FOOD & DRUG RETAILING--1.05%
Albertson's, Inc. 3,100 $ 59,520
CVS Corp. 3,200 89,696
Kroger Co.* 6,100 101,748
Safeway, Inc.* 3,600 73,656
SUPERVALU, Inc. 1,200 25,584
Sysco Corp. 5,200 156,208
Walgreen Co. 8,100 243,810
- -------------------------------------------------------------------------------
750,222
===============================================================================
FOOD PRODUCTS--1.29%
Archer-Daniels-Midland Co. 5,300 68,211
Campbell Soup Co. 3,300 80,850
ConAgra Foods, Inc. 4,300 101,480
General Mills, Inc. 2,900 137,489
Heinz, H.J. & Co. 2,800 92,344
Hershey Foods Corp. 1,100 76,626
Kellogg Co. 3,200 109,984
McCormick & Co., Inc. 1,200 32,640
Sara Lee Corp. 6,300 118,503
Wrigley, Wm. Jr. Co. 1,800 101,214
- -------------------------------------------------------------------------------
919,341
===============================================================================
GAS UTILITIES--0.27%
KeySpan Corp. 1,300 46,085
Kinder Morgan, Inc. 1,000 54,650
NiSource, Inc. 2,200 41,800
Sempra Energy 1,700 48,501
- -------------------------------------------------------------------------------
191,036
===============================================================================
HEALTH CARE EQUIPMENT &
SUPPLIES--1.92%
Applera Corp.--
Applied Biosystems Group 1,700 32,351
Baxter International, Inc. 4,800 124,800
Becton, Dickinson and Co. 2,100 81,585
Biomet, Inc. 2,100 60,186
Boston Scientific Corp.* 3,300 201,630
C.R. Bard, Inc. 400 28,524
Guidant Corp. 2,500 110,975
Medtronic, Inc. 9,700 465,309
</Table>
9
<Page>
<Table>
<Caption>
SECURITY DESCRIPTION SHARES VALUE
- -------------------------------------------------------------------------------
HEALTH CARE EQUIPMENT &
SUPPLIES--(CONCLUDED)
St. Jude Medical, Inc.* 1,400 $ 80,500
Stryker Corp. 1,600 110,992
Zimmer Holdings, Inc.* 1,600 72,080
- -------------------------------------------------------------------------------
1,368,932
===============================================================================
HEALTH CARE PROVIDERS &
SERVICES--1.77%
Aetna, Inc. 1,200 72,240
AmerisourceBergen Corp. 900 62,415
Anthem, Inc.* 1,100 84,865
Cardinal Health, Inc. 3,600 231,480
CIGNA Corp. 1,100 51,634
HCA, Inc. 4,100 131,364
Health Management Associates, Inc.,
Class A 1,900 35,055
Humana, Inc.* 1,400 21,140
IMS Health, Inc. 2,000 35,980
Manor Care, Inc.* 800 20,008
McKesson Corp. 2,300 82,202
Quest Diagnostics, Inc.* 800 51,040
Tenet Healthcare Corp.* 3,800 44,270
UnitedHealth Group, Inc. 4,700 236,175
Wellpoint Health Networks, Inc.* 1,200 101,160
- -------------------------------------------------------------------------------
1,261,028
===============================================================================
HOTELS, RESTAURANTS &
LEISURE--1.19%
Carnival Corp. 5,000 162,550
Darden Restaurants, Inc. 1,400 26,572
Harrah's
Entertainment, Inc.* 900 36,216
Hilton Hotels Corp. 3,100 39,649
International Game
Technology* 700 71,631
Marriott
International, Inc. 1,800 69,156
McDonald's Corp. 10,100 222,806
Starbucks Corp.* 3,100 76,012
Starwood Hotels &
Resorts Worldwide,
Inc., Class B 1,700 48,603
Wendy's International, Inc. 1,000 $ 28,970
Yum! Brands, Inc.* 2,300 67,988
- -------------------------------------------------------------------------------
850,153
===============================================================================
HOUSEHOLD DURABLES--0.51%
Black & Decker Corp. 700 30,415
Centex Corp. 500 38,895
Fortune Brands, Inc. 1,200 62,640
KB HOME 400 24,792
Leggett & Platt, Inc. 1,700 34,850
Maytag Corp. 700 17,094
Newell Rubbermaid, Inc. 2,200 61,600
Pulte Homes, Inc. 500 30,830
Stanley Works 800 22,080
Whirlpool Corp. 600 38,220
- -------------------------------------------------------------------------------
361,416
===============================================================================
HOUSEHOLD PRODUCTS--2.02%
Clorox Co. 1,800 76,770
Colgate-Palmolive Co. 4,300 249,185
Kimberly Clark Corp. 4,000 208,560
Procter & Gamble Co. 10,200 909,636
- -------------------------------------------------------------------------------
1,444,151
===============================================================================
INDUSTRIAL CONGLOMERATES--4.22%
3M Co. 3,100 399,838
General Electric Co. 79,200 2,271,456
Textron, Inc. 1,100 42,922
Tyco International Ltd. 15,900 301,782
- -------------------------------------------------------------------------------
3,015,998
===============================================================================
INSURANCE--4.60%
ACE Ltd. 2,100 72,009
AFLAC, Inc. 4,000 123,000
Allstate Corp. 5,600 199,640
Ambac Financial
Group, Inc. 800 53,000
American International
Group, Inc. 20,700 1,142,226
AON Corp. 2,500 60,200
Chubb Corp. 1,500 90,000
Cincinnati Financial Corp. 1,300 48,217
</Table>
10
<Page>
<Table>
<Caption>
SECURITY DESCRIPTION SHARES VALUE
- -------------------------------------------------------------------------------
INSURANCE--(CONCLUDED)
Hartford Financial Services Group, Inc. 2,200 $ 110,792
Jefferson-Pilot Corp. 1,200 49,752
John Hancock Financial Services, Inc. 2,300 70,679
Lincoln National Corp. 1,400 49,882
Loews Corp. 1,500 70,935
Marsh & McLennan Cos., Inc. 4,200 214,494
MBIA, Inc. 1,200 58,500
Metlife, Inc. 6,000 169,920
MGIC Investment Corp. 800 37,312
Progressive Corp. 1,700 124,270
Prudential Financial, Inc. 4,400 148,060
SAFECO Corp. 1,200 42,336
St. Paul Cos., Inc. 1,900 69,369
Torchmark Corp. 900 33,525
Travelers Property
Casualty Corp., Class B 8,000 126,160
UnumProvident Corp. 2,400 32,184
XL Capital Ltd., Class A 1,100 91,300
- -------------------------------------------------------------------------------
3,287,762
===============================================================================
INTERNET & CATALOG RETAIL--0.36%
eBay, Inc.* 2,500 260,450
===============================================================================
INTERNET SOFTWARE & SERVICES--0.22%
Yahoo!, Inc.* 4,800 157,248
===============================================================================
IT CONSULTING & SERVICES--0.32%
Computer Sciences Corp.* 1,500 57,180
Electronic Data Systems Corp. 3,800 81,510
SunGard Data Systems, Inc.* 2,300 59,593
Unisys Corp.* 2,700 33,156
- -------------------------------------------------------------------------------
231,439
===============================================================================
LEISURE EQUIPMENT & PRODUCTS--0.39%
Brunswick Corp. 900 22,518
Eastman Kodak Co. 2,300 62,905
Harley-Davidson, Inc. 2,400 95,664
Hasbro, Inc. 1,500 26,235
Mattel, Inc. 3,600 $ 68,112
- -------------------------------------------------------------------------------
275,434
===============================================================================
MACHINERY--1.20%
Caterpillar, Inc. 2,800 155,848
Danaher Corp. 1,200 81,660
Deere & Co. 1,900 86,830
Dover Corp. 1,700 50,932
Eaton Corp. 600 47,166
Illinois Tool Works, Inc. 2,500 164,625
Ingersoll Rand Co., Class A 1,400 66,248
ITT Industries, Inc. 800 52,368
Navistar International Corp. 600 19,578
PACCAR, Inc. 1,000 67,560
Pall Corp. 1,100 24,750
Parker-Hannifin Corp. 1,000 41,990
- -------------------------------------------------------------------------------
859,555
===============================================================================
MEDIA--4.18%
AOL Time Warner, Inc.* 35,700 574,413
Clear Channel Communications, Inc.* 4,900 207,711
Comcast Corp., Class A* 17,900 540,222
Disney, Walt Co. 16,300 321,925
Dow Jones & Co., Inc. 800 34,424
Gannett Co., Inc. 2,200 168,982
Interpublic Group Cos., Inc. 3,200 42,816
Knight-Ridder, Inc. 700 48,251
McGraw-Hill Cos., Inc. 1,600 99,200
New York Times Co., Class A 1,300 59,150
Omnicom Group, Inc. 1,500 107,550
Tribune Co. 2,500 120,750
Univision Communications, Inc., Class A* 1,900 57,760
Viacom, Inc., Class B* 13,900 606,874
- -------------------------------------------------------------------------------
2,990,028
===============================================================================
</Table>
11
<Page>
<Table>
<Caption>
SECURITY DESCRIPTION SHARES VALUE
- -------------------------------------------------------------------------------
METALS & MINING--0.55%
Alcoa, Inc. 6,800 $ 173,400
Freeport-McMoRan Copper & Gold,
Inc., Class B(1) 1,300 31,850
Newmont Mining Corp. (Holding Co.) 3,200 103,872
Nucor Corp. 700 34,195
Phelps Dodge Corp.* 800 30,672
United States Steel Corp. 1,000 16,370
- -------------------------------------------------------------------------------
390,359
===============================================================================
MULTI-LINE RETAIL--3.89%
Big Lots, Inc.* 1,000 15,040
Costco Wholesale Corp.* 3,600 131,760
Dollar General Corp. 2,700 49,302
Family Dollar Stores, Inc. 1,400 53,410
Federated Department Stores, Inc. 1,600 58,960
J.C. Penney Co., Inc. (Holding Co.) 2,300 38,755
Kohl's Corp.* 2,700 138,726
May Department Stores Co. 2,400 53,424
Nordstrom, Inc. 1,200 23,424
Sears, Roebuck & Co. 2,500 84,100
Target Corp. 7,200 272,448
Wal-Mart Stores, Inc. 34,700 1,862,349
- -------------------------------------------------------------------------------
2,781,698
===============================================================================
MULTI-UTILITIES--0.38%
AES Corp.* 4,900 31,115
Calpine Corp.(1)* 3,200 21,120
Centerpoint Energy, Inc. 2,600 21,190
Duke Energy Corp. 7,200 143,640
Dynegy, Inc., Class A 3,100 13,020
Mirant Corp.* 3,600 10,440
Williams Cos., Inc. 4,200 33,180
- -------------------------------------------------------------------------------
273,705
===============================================================================
OFFICE ELECTRONICS--0.09%
Xerox Corp.* 6,000 63,540
===============================================================================
OIL & GAS--5.01%
Amerada Hess Corp. 800 $ 39,344
Anadarko Petroleum Corp. 2,000 88,940
Apache Corp. 1,300 84,578
Burlington Resources, Inc. 1,600 86,512
ChevronTexaco Corp. 8,500 613,700
ConocoPhillips 5,400 295,920
Devon Energy Corp. 1,900 101,460
El Paso Corp.(1) 4,900 39,592
EOG Resources, Inc. 900 37,656
Exxon Mobil Corp. 52,800 1,896,048
Kerr-McGee Corp. 900 40,320
Marathon Oil Corp. 2,600 68,510
Occidental Petroleum Corp. 3,100 104,005
Sunoco, Inc. 700 26,418
Unocal Corp. 2,100 60,249
- -------------------------------------------------------------------------------
3,583,252
===============================================================================
PAPER & FOREST PRODUCTS--0.45%
Georgia-Pacific Corp. 2,200 41,690
International Paper Co. 3,900 139,347
MeadWestvaco Corp. 1,800 44,460
Weyerhaeuser Co. 1,800 97,200
- -------------------------------------------------------------------------------
322,697
===============================================================================
PERSONAL PRODUCTS--0.56%
Alberto-Culver Co., Class B 500 25,550
Avon Products, Inc. 1,900 118,180
Gillette Co. 8,100 258,066
- -------------------------------------------------------------------------------
401,796
===============================================================================
PHARMACEUTICALS--9.82%
Abbott Laboratories 12,400 542,624
Allergan, Inc. 1,100 84,810
Bristol-Myers Squibb Co. 15,400 418,110
Eli Lilly & Co. 8,900 613,833
Forest Laboratories, Inc.* 2,900 158,775
Johnson & Johnson 23,500 1,214,950
King Pharmaceuticals, Inc.* 2,000 29,520
</Table>
12
<Page>
<Table>
<Caption>
SECURITY DESCRIPTION SHARES VALUE
- -------------------------------------------------------------------------------
PHARMACEUTICALS--(CONCLUDED)
Merck & Co., Inc. 17,800 $ 1,077,790
Pfizer, Inc. 62,600 2,137,790
Schering-Plough Corp. 11,700 217,620
Watson Pharmaceuticals, Inc.* 900 36,333
Wyeth Pharmaceuticals 10,600 482,830
- -------------------------------------------------------------------------------
7,014,985
===============================================================================
REAL ESTATE--0.38%
Equity Office
Properties Trust 3,500 94,535
Equity Residential
Properties Trust 2,500 64,875
Plum Creek Timber
Co., Inc. 1,700 44,115
Simon Property
Group, Inc. 1,700 66,351
- -------------------------------------------------------------------------------
269,876
===============================================================================
ROAD & RAIL--0.44%
Burlington Northern
Santa Fe Corp. 3,000 85,320
CSX Corp. 1,800 54,162
Norfolk Southern Corp. 3,100 59,520
Union Pacific Corp. 2,000 116,040
- -------------------------------------------------------------------------------
315,042
===============================================================================
SEMICONDUCTOR EQUIPMENT &
PRODUCTS--3.27%
Advanced Micro
Devices, Inc.* 2,900 18,589
Altera Corp.* 3,100 50,840
Analog Devices, Inc.* 2,900 100,978
Applied Materials, Inc.* 13,200 209,352
Applied Micro
Circuits Corp.* 2,500 15,125
Broadcom Corp.,
Class A* 2,200 54,802
Intel Corp. 51,800 1,076,611
KLA-Tencor Corp.* 1,500 69,735
Linear Technology Corp. 2,500 80,525
LSI Logic Corp.* 3,100 21,948
Maxim Integrated
Products, Inc. 2,600 88,894
Micron Technology, Inc.* 4,900 $ 56,987
National Semiconductor Corp.* 1,500 29,580
Novellus Systems, Inc.* 1,200 43,945
NVIDIA Corp.* 1,300 29,913
PMC-Sierra, Inc.* 1,400 16,422
QLogic Corp.* 800 38,664
Teradyne, Inc.* 1,500 25,965
Texas Instruments, Inc. 13,700 241,120
Xilinx, Inc.* 2,700 68,337
- -------------------------------------------------------------------------------
2,338,332
===============================================================================
SOFTWARE--4.71%
Adobe Systems, Inc. 1,900 60,933
Autodesk, Inc. 1,000 16,160
BMC Software, Inc.* 1,900 31,027
Citrix Systems, Inc.* 1,300 26,468
Computer Associates
International, Inc. 4,600 102,488
Compuware Corp.* 3,100 17,887
Electronic Arts, Inc.* 1,200 88,788
Intuit, Inc.* 1,600 71,248
Mercury Interactive
Corp.* 700 27,027
Microsoft Corp. 85,200 2,181,972
Novell, Inc.* 3,300 10,164
Oracle Corp.* 41,600 500,032
PeopleSoft, Inc.* 2,600 45,734
Siebel Systems, Inc.* 4,000 38,160
Symantec Corp.* 1,200 52,632
Veritas Software Co.* 3,300 94,611
- -------------------------------------------------------------------------------
3,365,331
===============================================================================
SPECIALTY RETAIL--2.38%
AutoNation, Inc.* 2,400 37,728
AutoZone, Inc.* 700 53,179
Bed, Bath & Beyond, Inc.* 2,400 93,144
Best Buy Co., Inc.* 2,600 114,192
Circuit City Stores-
Circuit City Group 1,800 15,840
Gap, Inc. 7,100 133,196
</Table>
13
<Page>
<Table>
<Caption>
SECURITY DESCRIPTION SHARES VALUE
- -------------------------------------------------------------------------------
SPECIALTY RETAIL--(CONCLUDED)
Home Depot, Inc. 18,200 $ 602,784
Limited Brands 4,200 65,100
Lowe's Cos., Inc. 6,200 266,290
Office Depot, Inc.* 2,500 36,275
RadioShack Corp. 1,400 36,834
Sherwin-Williams Co. 1,300 34,944
Staples, Inc.* 3,900 71,565
Tiffany & Co. 1,200 39,216
TJX Cos., Inc. 4,100 77,244
Toys "R" Us, Inc.* 1,800 21,816
- -------------------------------------------------------------------------------
1,699,347
===============================================================================
TEXTILES & APPAREL--0.29%
Jones Apparel
Group, Inc.* 1,100 32,186
Liz Claiborne, Inc. 900 31,725
Nike, Inc., Class B 2,100 112,329
V. F. Corp. 1,000 33,970
- -------------------------------------------------------------------------------
210,210
===============================================================================
TOBACCO--1.12%
Altria Group, Inc. 16,000 $ 727,040
R.J. Reynolds Tobacco
Holdings, Inc. 800 29,768
UST, Inc. 1,300 45,539
- -------------------------------------------------------------------------------
802,347
===============================================================================
TRADING COMPANIES &
DISTRIBUTORS--0.12%
Genuine Parts Co. 1,500 48,015
W.W. Grainger, Inc. 800 37,408
- -------------------------------------------------------------------------------
85,423
===============================================================================
WIRELESS TELECOMMUNICATION
SERVICES--0.52%
AT&T Wireless
Services, Inc.* 21,500 176,515
Nextel Communications,
Inc., Class A* 8,200 148,256
Sprint Corp.
(PCS Group)* 8,200 47,150
- -------------------------------------------------------------------------------
371,921
===============================================================================
Total Common Stocks
(cost--$91,171,553) 71,438,883
===============================================================================
<Caption>
MATURITY INTEREST
SHARES DATE RATE
- ---------- -------- --------
INVESTMENTS OF CASH COLLATERAL FROM SECURITIES LOANED--0.24%
MONEY MARKET FUND--0.24%
168,200 UBS Private Money Market
Fund LLC (cost--$168,200) 07/01/03 1.124%+ 168,200
Total Investments (cost--$91,339,753)--100.21% 71,607,083
Liabilities in excess of other assets--(0.21)% (147,784)
- -------------------------------------------------------------------------------------------------
Net Assets--100.00% $ 71,459,299
=================================================================================================
</Table>
* Non-income producing security.
(1) Security, or portion thereof, was on loan at June 30, 2003.
(2) Includes 500 Contingent Value Obligations valued at zero.
+ Interest rate shown reflects yield at June 30, 2003.
See accompanying notes to financial statements
14
<Page>
Statement of Assets and Liabilities -- June 30, 2003 (unaudited)
<Table>
ASSETS:
Investment in securities, at value (cost--$91,339,753)* $ 71,607,083
Receivable for investments sold 381,323
Dividends receivable 89,413
Other assets 953
Total assets 72,078,772
LIABILITIES:
Payable to custodian 336,297
Payable for cash collateral from securities loaned 168,200
Payable to affiliates 61,333
Accrued expenses and other liabilities 53,643
Total liabilities 619,473
NET ASSETS:
Beneficial interest--$0.001 par value (unlimited amount authorized) 116,254,060
Accumulated undistributed net investment income 292,350
Accumulated net realized loss from investment transactions (25,354,441)
Net unrealized depreciation of investments (19,732,670)
- ---------------------------------------------------------------------------------------------
Net assets $ 71,459,299
=============================================================================================
CLASS H:
Net assets $ 19,603,953
Shares outstanding 1,826,043
Net asset value, offering price and redemption value per share $ 10.74
CLASS I:
Net assets $ 51,855,346
Shares outstanding 4,835,571
Net asset value, offering price and redemption value per share $ 10.72
=============================================================================================
</Table>
* Includes $158,786 of investments in securities on loan, at value.
See accompanying notes to financial statements
15
<Page>
Statement of Operations
<Table>
<Caption>
FOR THE
SIX MONTHS
ENDED
JUNE 30, 2003
(UNAUDITED)
- ---------------------------------------------------------------------------------------------
INVESTMENT INCOME:
Dividends $ 609,800
Interest 359
610,159
EXPENSES:
Investment advisory and administration fees 169,276
Distribution fees--Class I 60,920
Reports and notices to shareholders 30,451
Professional fees 29,751
Custody and accounting 20,313
Transfer agency and related services fees 1,500
Trustees' fees 642
Other expenses 5,863
318,716
Net investment income 291,443
REALIZED AND UNREALIZED GAINS (LOSSES) FROM INVESTMENT ACTIVITIES:
Net realized loss from investment activities (3,700,825)
Net change in unrealized appreciation/depreciation of investments 10,682,672
Net realized and unrealized gain from investment activities 6,981,847
- ---------------------------------------------------------------------------------------------
Net increase in net assets resulting from operations $ 7,273,290
=============================================================================================
</Table>
See accompanying notes to financial statements
16
<Page>
Statement of Changes in Net Assets
<Table>
<Caption>
FOR THE
SIX MONTHS FOR THE
ENDED YEAR ENDED
JUNE 30, 2003 DECEMBER 31,
(UNAUDITED) 2002
- ---------------------------------------------------------------------------------------------
FROM OPERATIONS:
Net investment income $ 291,443 $ 678,876
Net realized losses from investment activities (3,700,825) (15,452,200)
Net change in unrealized appreciation/depreciation
of investments 10,682,672 (10,600,342)
Net increase (decrease) in net assets resulting
from operations 7,273,290 (25,373,666)
DIVIDENDS TO SHAREHOLDERS FROM:
Net investment income--Class H (240,176) (212,147)
Net investment income--Class I (431,950) (397,516)
(672,126) (609,663)
FROM BENEFICIAL INTEREST TRANSACTIONS:
Net proceeds from the sale of shares 2,342,815 5,880,228
Cost of shares repurchased (8,169,621) (28,925,120)
Proceeds from dividends reinvested 672,126 609,663
Net decrease in net assets from beneficial
interest transactions (5,154,680) (22,435,229)
Net increase (decrease) in net assets 1,446,484 (48,418,558)
NET ASSETS:
Beginning of period 70,012,815 118,431,373
- ---------------------------------------------------------------------------------------------
End of period (including accumulated undistributed
net investment income of $292,350 and
$673,033, respectively) $ 71,459,299 $ 70,012,815
=============================================================================================
</Table>
See accompanying notes to financial statements
17
<Page>
Notes to Financial Statements (unaudited)
ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES
UBS Series Trust--Tactical Allocation Portfolio (the "Portfolio") is a
diversified portfolio of UBS Series Trust (the "Fund"). The Fund is organized
under Massachusetts law pursuant to an Amended and Restated Declaration of Trust
dated February 11, 1998, as amended, and is registered with the Securities and
Exchange Commission under the Investment Company Act of 1940, as amended, as an
open-end management investment company. The Fund operates as a series company
currently offering one portfolio. Shares of the Portfolio are offered to
insurance company separate accounts which fund certain variable annuity
contracts.
Currently, the Portfolio offers Class H and Class I shares. Each class
represents interests in the same assets of the Portfolio, and the classes are
identical except for differences in their distribution charges. Both classes
have equal voting privileges except that Class I has exclusive voting rights
with respect to its distribution plan. Class H has no distribution plan.
The preparation of financial statements in accordance with accounting principles
generally accepted in the United States requires the Fund's management to make
estimates and assumptions that affect the reported amounts and disclosures in
the financial statements. Actual results could differ from those estimates. The
following is a summary of significant accounting policies:
VALUATION OF INVESTMENTS--The Portfolio calculates net asset values based on the
current market value for its portfolio's securities. The Portfolio normally
obtains market values for its securities from independent pricing sources.
Independent pricing sources may use reported last sale prices, current market
quotations or valuations from computerized "matrix" systems that derive values
based on comparable securities. Securities traded in the over-the-counter
("OTC") market and listed on The Nasdaq Stock Market, Inc. ("Nasdaq") normally
are valued at the NASDAQ Official Closing Price. Other OTC securities are valued
at the last bid price available prior to valuation. Securities which are listed
on U.S. and foreign stock exchanges normally are valued at the last sale price
on the day the securities are valued or, lacking any sales on such day, at the
last available bid price. In cases where securities are traded on more than one
exchange, the securities are valued on the exchange designated as the primary
market by UBS Global Asset Management (US) Inc. ("UBS Global AM"), the
investment advisor and administrator of the Portfolio. UBS Global AM is an
indirect wholly owned asset management subsidiary of UBS AG, an internationally
diversified organization with headquarters in Zurich, Switzerland and operations
in many areas of the financial services industry. If a market value is not
available from an independent pricing source for a particular security, that
security is valued at fair value as determined in good faith by or under the
direction of the Fund's Board of Trustees (the "Board"). The amortized cost
method of valuation, which approximates market value, generally is used to value
18
<Page>
short-term debt-instruments with sixty days or less remaining to maturity,
unless the Board determines that this does not represent fair value.
REPURCHASE AGREEMENTS--The Portfolio may purchase securities or other
obligations from a bank or securities dealer (or its affiliate), subject to the
seller's agreement to repurchase them at an agreed upon date (or upon demand)
and price. The Portfolio maintains custody of the underlying obligations prior
to their repurchase, either through its regular custodian or through a special
"tri-party" custodian or sub-custodian that maintains a separate account for
both the Portfolio and its counterparty. The underlying collateral is valued
daily on a mark-to-market basis to ensure that the value, including accrued
interest, is at least equal to the repurchase price. In the event of default of
the obligation to repurchase, the Portfolio generally has the right to liquidate
the collateral and apply the proceeds in satisfaction of the obligation.
Repurchase agreements involving obligations other than U.S. government
securities (such as commercial paper, corporate bonds and mortgage loans) may be
subject to special risks and may not have the benefit of certain protections in
the event of the counterparty's insolvency. If the seller (or seller's
guarantor, if any) becomes insolvent, the Portfolio may suffer delays, costs and
possible losses in connection with the disposition or retention of the
collateral. Under certain circumstances, in the event of default or bankruptcy
by the other party to the agreement, realization and/or retention of the
collateral may be subject to legal proceedings. The Portfolio may participate in
joint repurchase agreement transactions with other funds managed, advised or
sub-advised by UBS Global AM.
INVESTMENT TRANSACTIONS AND INVESTMENT INCOME--Investment transactions are
recorded on the trade date. Realized gains and losses from investment
transactions are calculated using the identified cost method. Dividend income is
recorded on the ex-dividend date ("ex-date"). Interest income is recorded on an
accrual basis. Discounts are accreted and premiums are amortized as adjustments
to interest income and the identified cost of investments.
Income, expenses (excluding class-specific expenses) and realized/unrealized
gains/losses are allocated proportionately to each class of shares based upon
the relative net asset value of outstanding shares (or the value of
dividend-eligible shares, as appropriate) of each class at the beginning of the
day (after adjusting for current capital share activity of the respective
classes). Class-specific expenses are charged directly to the applicable class
of shares.
DIVIDENDS AND DISTRIBUTIONS--Dividends and distributions to shareholders are
recorded on the ex-date. The amount of dividends and distributions is determined
in accordance with federal income tax regulations, which may differ from
accounting principles generally accepted in the United States. These "book/tax"
differences are either considered temporary or permanent in nature. To the
19
<Page>
extent these differences are permanent in nature, such amounts are reclassified
within the capital accounts based on their federal tax-basis treatment;
temporary differences do not require reclassification.
INVESTMENT ADVISOR AND ADMINISTRATOR
The Board has approved an Investment Advisory and Administration Contract
("Advisory Contract"), under which UBS Global AM serves as investment advisor
and administrator of the Portfolio. In accordance with the Advisory Contract,
the Portfolio pays UBS Global AM an investment advisory and administration fee,
which is accrued daily and paid monthly, at an annual rate of 0.50% of the
Portfolio's average daily net assets. At June 30, 2003, the Portfolio owed UBS
Global AM $29,999 in investment advisory and administration fees.
For the six months ended June 30, 2003, the Portfolio did not pay any brokerage
commissions to UBS Financial Services Inc., an indirect wholly owned subsidiary
of UBS AG, or any other affiliated broker-dealer for transactions executed on
behalf of the Portfolio.
DISTRIBUTION PLAN
Class I shares are offered to insurance company separate accounts where the
related insurance companies receive payments for their services in connection
with the distribution of the Portfolio's Class I shares. Under the plan of
distribution, the Portfolio pays UBS Global AM a monthly distribution fee at the
annual rate of 0.25% of the average daily net assets of Class I shares. UBS
Global AM pays the entire distribution fee to the insurance companies. At June
30, 2003, the Portfolio owed UBS Global AM $31,323 in distribution fees.
SECURITIES LENDING
The Portfolio may lend securities up to 33 1/3% of its total assets to qualified
broker-dealers or institutional investors. The loans are secured at all times by
cash, cash equivalents or U.S. government securities in an amount at least equal
to the market value of the securities loaned, plus accrued interest and
dividends, determined on a daily basis and adjusted accordingly. The Portfolio
will regain record ownership of loaned securities to exercise certain beneficial
rights; however, the Portfolio may bear the risk of delay in recovery of, or
even loss of rights in, the securities loaned should the borrower fail
financially. The Portfolio receives compensation, which is included in interest
income, for lending its securities from interest or dividends earned on the
cash, cash equivalents or U.S. government securities held as collateral, net of
fee rebates paid to the borrower plus reasonable administrative and custody
fees. UBS Financial Services Inc. and other affiliated broker-dealers have been
approved as borrowers under the Portfolio's securities lending program. For the
six months ended June 30, 2003, the Portfolio earned $210 for lending its
20
<Page>
securities, and UBS Financial Services Inc. or UBS Securities LLC earned $70 in
compensation as the Portfolio's lending agent. At June 30, 2003, the Portfolio
owed UBS Securities LLC $11 in compensation as the Portfolio's lending agent.
BANK LINE OF CREDIT
The Portfolio participated with other funds managed, advised or sub-advised by
UBS Global AM in a $300 million committed credit facility ("Facility") with UBS
AG, Stamford Branch, to be utilized for temporary financing until the settlement
of sales or purchases of portfolio securities, the repurchase or redemption of
shares of the Portfolio at the request of the shareholders and other temporary
or emergency purposes. Under the Facility arrangement, the Portfolio had agreed
to pay a commitment fee, pro rata, based on the relative asset size of the funds
in the Facility. Interest would be charged to the Portfolio at rates based on
prevailing market rates in effect at the time of borrowings. For the six months
ended June 30, 2003, the Portfolio did not borrow under the Facility. For the
six months ended June 30, 2003, the Portfolio paid a commitment fee of $482 to
UBS AG.
FEDERAL TAX STATUS
At June 30, 2003, the components of net unrealized depreciation of investments
were as follows:
<Table>
Gross appreciation (investments having an excess of value over cost) $ 4,356,673
Gross depreciation (investments having an excess of cost over value) (24,089,343)
- --------------------------------------------------------------------------------------------
Net unrealized depreciation of investments $ (19,732,670)
============================================================================================
</Table>
For the six months ended June 30, 2003, aggregate purchases and sales of
portfolio securities, excluding short-term securities, were $1,315,940 and
$6,844,224, respectively.
The Portfolio intends to distribute substantially all of its taxable income and
to comply with the other requirements of the Internal Revenue Code applicable to
regulated investment companies. Accordingly, no provision for federal income
taxes is required. In addition, by distributing during each calendar year,
substantially all of its net investment income, realized capital gains and
certain other amounts, if any, the Portfolio intends not to be subject to a
federal excise tax.
The tax character of distributions paid during the fiscal year ended December
31, 2002 was as follows:
<Table>
<Caption>
DISTRIBUTIONS PAID FROM: 2002
- --------------------------------------------------------------------------------------------
Ordinary income $ 609,663
============================================================================================
</Table>
The tax character of distributions paid and the components of accumulated
earnings (deficit) on a tax basis for the current fiscal year will be calculated
for the Portfolio after the Portfolio's fiscal year end at December 31, 2003.
21
<Page>
At December 31, 2002, the Portfolio had a capital loss carryforward of
$14,062,333. This loss carryforward is available as a reduction, to the extent
provided in the regulations, of any future net realized capital gains and will
expire as follows: $863,515 will expire December 31, 2009 and $13,198,818 will
expire December 31, 2010. To the extent that such losses are used to offset
future realized capital gains, it is probable that the gains so offset will not
be distributed. Also, in accordance with U.S. Treasury regulations, the
Portfolio has elected to defer $3,697,892 of net realized capital losses arising
after October 31, 2002. Such losses are treated for tax purposes as arising on
January 1, 2003.
SHARES OF BENEFICIAL INTEREST
There is an unlimited number of $0.001 par value shares of beneficial interest
authorized. Transactions in shares of beneficial interest were as follows:
<Table>
<Caption>
CLASS H CLASS I
SIX MONTHS ENDED ---------------------------- ---------------------------
JUNE 30, 2003: SHARES AMOUNT SHARES AMOUNT
- ----------------------------------------------------------------------------------------------
Shares sold 76,447 $ 746,127 162,778 $ 1,596,688
Shares repurchased (297,032) (2,908,293) (537,820) (5,261,328)
Dividends reinvested 24,951 240,176 44,854 431,950
- ----------------------------------------------------------------------------------------------
Net decrease (195,634) $ (1,921,990) (330,188) $ (3,232,690)
==============================================================================================
<Caption>
YEAR ENDED
DECEMBER 31, 2002:
Shares sold 36,481 $ 393,090 490,622 $ 5,487,138
Shares repurchased (592,748) (6,736,327) (2,121,694) (22,188,793)
Dividends reinvested 17,094 212,147 32,084 397,516
- ----------------------------------------------------------------------------------------------
Net decrease (539,173) $ (6,131,090) (1,598,988) $ (16,304,139)
==============================================================================================
</Table>
22
<Page>
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23
<Page>
Financial Highlights
Selected data for a share of beneficial interest outstanding throughout each
period is presented below:
<Table>
<Caption>
CLASS H
--------------------------------------------------------------------------------------------
FOR THE FOR THE PERIOD
SIX MONTHS SEPTEMBER 28,
ENDED FOR THE YEARS ENDED DECEMBER 31, 1998+ THROUGH
JUNE 30, 2003 ------------------------------------------------------- DECEMBER 31,
(UNAUDITED) 2002 2001 2000 1999 1998
- ----------------------------------------------------------------------------------------------------------------------------------
NET ASSET VALUE,
BEGINNING OF PERIOD $ 9.77 $ 12.73 $ 15.83 $ 16.49 $ 14.91 $ 12.00
Net investment income 0.07 0.10@ 0.08 0.40@ 0.11@ 0.02
Net realized and
unrealized gains
(losses) from
investment transactions 1.02 (2.97)@ (2.02) (0.71)@ 2.64@ 2.99
Net increase (decrease)
from investment
operations 1.09 (2.87) (1.94) (0.31) 2.75 3.01
Dividends from net
investment income (0.12) (0.09) (0.33) (0.01) (0.06) (0.02)
Distributions from net
realized gains from
investment transactions -- -- (0.83) (0.34) (1.11) (0.08)
Total dividends and
distributions to
shareholders (0.12) (0.09) (1.16) (0.35) (1.17) (0.10)
NET ASSET VALUE,
END OF PERIOD $ 10.74 $ 9.77 $ 12.73 $ 15.83 $ 16.49 $ 14.91
TOTAL INVESTMENT RETURN(1) 11.34% (22.68)% (12.39)% (1.93)% 18.43% 24.98%
RATIOS/SUPPLEMENTAL
DATA:
Net assets,
end of period (000's) $ 19,604 $ 19,743 $ 32,607 $ 41,212 $ 36,714 $ 22,494
Expenses to average
net assets, net of
waivers from advisor 0.76%* 0.66% 0.67% 0.72% 0.74% 0.95%*
Expenses to average
net assets, before
waivers from advisor 0.76%* 0.66% 0.67% 0.73% 0.74% 0.95%*
Net investment income
to average net assets,
net of waivers from advisor 1.04%* 0.91% 0.67% 2.50% 0.71% 0.77%*
Net investment income
to average net assets,
before waivers from advisor 1.04%* 0.91% 0.67% 2.49% 0.71% 0.77%*
- ----------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover 2% 5% 10% 166% 110% 6%
==================================================================================================================================
</Table>
+ Commencement of operations.
++ Commencement of issuance of shares.
* Annualized.
@ Calculated using average monthly shares outstanding for the period.
(1) Total investment return is calculated assuming a $10,000 investment on the
first day of each period reported, reinvestment of all dividends and
distributions, if any, at net asset value on the ex-dividend dates, and a
sale at net asset value on the last day of each period reported. The
figures do not include additional contract level charges; results would be
lower if they were included. Total investment return for periods of less
than one year has not been annualized.
24
<Page>
<Table>
<Caption>
CLASS I
--------------------------------------------------------------------------------
FOR THE FOR THE PERIOD
SIX MONTHS JANUARY 5, 1999++
ENDED FOR THE YEARS ENDED DECEMBER 31, THROUGH
JUNE 30, 2003 ---------------------------------------- DECEMBER 31,
(UNAUDITED) 2002 2001 2000 1999
- ----------------------------------------------------------------------------------------------------------------------
NET ASSET VALUE,
BEGINNING OF PERIOD $ 9.73 $ 12.69 $ 15.78 $ 16.48 $ 14.89
Net investment income 0.04 0.07@ 0.04 0.36@ 0.11@
Net realized and
unrealized gains
(losses) from
investment transactions 1.04 (2.97)@ (2.00) (0.71)@ 2.65@
Net increase (decrease)
from investment
operations 1.08 (2.90) (1.96) (0.35) 2.76
Dividends from net
investment income (0.09) (0.06) (0.30) (0.01) (0.06)
Distributions from net
realized gains from
investment transactions -- -- (0.83) (0.34) (1.11)
Total dividends and
distributions to
shareholders (0.09) (0.06) (1.13) (0.35) (1.17)
NET ASSET VALUE,
END OF PERIOD $ 10.72 $ 9.73 $ 12.69 $ 15.78 $ 16.48
TOTAL INVESTMENT RETURN(1) 11.19% (22.95)% (12.55)% (2.18)% 18.52%
RATIOS/SUPPLEMENTAL
DATA:
Net assets,
end of period (000's) $ 51,855 $ 50,270 $ 85,825 $ 84,787 $ 54,413
Expenses to average
net assets, net of
waivers from advisor 1.01%* 0.91% 0.92% 0.94% 0.74%*
Expenses to average
net assets, before
waivers from advisor 1.01%* 0.91% 0.92% 0.98% 0.99%*
Net investment income
to average net assets,
net of waivers from advisor 0.79%* 0.66% 0.42% 2.27% 0.81%*
Net investment income
to average net assets,
before waivers from advisor 0.79%* 0.66% 0.42% 2.23% 0.56%*
- ----------------------------------------------------------------------------------------------------------------------
Portfolio turnover 2% 5% 10% 166% 110%
======================================================================================================================
</Table>
25
<Page>
General Information (unaudited)
PROXY VOTING POLICIES AND PROCEDURES
You may obtain a description of the Fund's proxy voting policies and procedures,
without charge, upon request by contacting the Fund directly at 1-800-647 1568
or online on the Fund's Web site www.ubs.com/ubsglobalam-proxy.
26
<Page>
TRUSTEES
Brian M. Storms
CHAIRMAN
Margo N. Alexander
Richard Q. Armstrong
David J. Beaubien
Richard R. Burt
Meyer Feldberg
Frederic V. Malek
Carl W. Schafer
William D. White
PRINCIPAL OFFICERS
Joseph A. Varnas
PRESIDENT
Amy R. Doberman
VICE PRESIDENT AND SECRETARY
Paul H. Schubert
VICE PRESIDENT AND TREASURER
T. Kirkham Barneby
VICE PRESIDENT
W. Douglas Beck
VICE PRESIDENT
INVESTMENT ADVISOR AND
ADMINISTRATOR
UBS Global Asset Management (US) Inc.
51 West 52nd Street
New York, New York 10019-6114
THE FINANCIAL INFORMATION INCLUDED HEREIN IS TAKEN FROM THE RECORDS OF THE
PORTFOLIO WITHOUT EXAMINATION BY INDEPENDENT AUDITORS WHO DO NOT EXPRESS AN
OPINION THEREON.
THIS REPORT IS NOT TO BE USED IN CONNECTION WITH THE OFFERING OF SHARES OF THE
PORTFOLIO UNLESS ACCOMPANIED OR PRECEDED BY AN EFFECTIVE PROSPECTUS.
(C) 2003 UBS Global Asset Management (US) Inc.
All rights reserved.
<Page>
[UBS LOGO]
Presorted
UBS GLOBAL ASSET MANAGEMENT Standard
51 West 52nd Street U.S.Postage
New York, New York 10019 PAID
Smithtown, NY
Permit 700
<Page>
ITEM 2. CODE OF ETHICS.
Form N-CSR disclosure requirement not yet effective with respect to the
registrant.
ITEM 3. AUDIT COMMITTEE FINANCIAL EXPERT.
Form N-CSR disclosure requirement not yet effective with respect to the
registrant.
ITEM 4. PRINCIPAL ACCOUNTANT FEES AND SERVICES.
Form N-CSR disclosure requirement not yet effective with respect to the
registrant.
ITEM 5. AUDIT COMMITTEE OF LISTED REGISTRANTS.
Not applicable to the registrant.
ITEM 6. [RESERVED BY SEC FOR FUTURE USE. ]
ITEM 7. DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR CLOSED - END
MANAGEMENT INVESTMENT COMPANIES.
Not applicable to the registrant.
ITEM 8. [RESERVED BY SEC FOR FUTURE USE. ]
ITEM 9. CONTROLS AND PROCEDURES.
(a) The registrant's principal executive officer and principal financial
officer have concluded that the registrant's disclosure controls and
procedures (as defined in Rule 30a-3(c) under the Investment Company Act
of 1940, as amended) are effective based on their evaluation of these
controls and procedures as of a date within 90 days of the filing date of
this document.
<Page>
(b) The registrant's principal executive officer and principal financial
officer are aware of no changes in the registrant's internal control over
financial reporting that occurred during the registrant's most recent
fiscal half-year that has materially affected, or is reasonably likely to
materially affect, the registrant's internal control over financial
reporting.
ITEM 10. EXHIBITS.
(a)(1) Code of Ethics - Form N-CSR requirement not yet effective with
respect to the registrant.
(a)(2) Certifications of principal executive officer and principal
financial officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 is
attached hereto as Exhibit 99.CERT.
(b) Certifications of principal executive officer and principal financial
officer pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 is attached
hereto as Exhibit 99.906CERT.
<Page>
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934 and the
Investment Company Act of 1940, the registrant has duly caused this report to be
signed on its behalf by the undersigned, thereunto duly authorized.
UBS SERIES TRUST
By: /s/ Joseph A. Varnas
--------------------
Joseph A. Varnas
President
Date: September 5, 2003
-----------------
Pursuant to the requirements of the Securities Exchange Act of 1934 and the
Investment Company Act of 1940, this report has been signed below by the
following persons on behalf of the registrant and in the capacities and on the
dates indicated.
By: /s/ Joseph A. Varnas
--------------------
Joseph A. Varnas
President
Date: September 5, 2003
-----------------
By: /s/ Paul H. Schubert
--------------------
Paul H. Schubert
<Page>
Treasurer
Date: September 5, 2003
-----------------