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: 811-21024

Active Assets Institutional Government Securities Trust
(Exact name of registrant as specified in charter)

522 Fifth Avenue, New York, New York 10036
(Address of principal executive offices) (Zip code)

Ronald E. Robison
522 Fifth Avenue, New York, New York 10036
(Name and address of agent for service)

Registrant's telephone number, including area code: 212-296-6990

Date of fiscal year end: June 30, 2008

Date of reporting period: December 31, 2007

Item 1 - Report to Shareholders

Welcome, Shareholder:
In this report, you'll learn about how your investment in Active Assets
Institutional Government Securities Trust performed during the semiannual
period. We will provide an overview of the market conditions, and discuss some
of the factors that affected performance during the reporting period. In
addition, this report includes the Fund's financial statements and a list of
Fund investments.

THIS MATERIAL MUST BE PRECEDED OR ACCOMPANIED BY A PROSPECTUS FOR THE FUND BEING
OFFERED.

MARKET FORECASTS PROVIDED IN THIS REPORT MAY NOT NECESSARILY COME TO PASS. THERE
IS NO ASSURANCE THAT A MUTUAL FUND WILL ACHIEVE ITS INVESTMENT OBJECTIVE. AN
INVESTMENT IN A MONEY MARKET FUND IS NOT INSURED OR GUARANTEED BY THE FEDERAL
DEPOSIT INSURANCE CORPORATION OR ANY OTHER GOVERNMENT AGENCY. ALTHOUGH THE FUND
SEEKS TO PRESERVE THE VALUE OF AN INVESTMENT AT $1.00 PER SHARE, IT IS POSSIBLE
TO LOSE MONEY BY INVESTING IN THE FUND. PLEASE SEE THE PROSPECTUS FOR MORE
COMPLETE INFORMATION ON INVESTMENT RISKS.

FUND REPORT

For the six months ended December 31, 2007

MARKET CONDITIONS

Throughout most of the fiscal period under review, the majority of home sales
and housing-related statistics were consistently lower than expected. New home
sales for the month of November reached the lowest level since April 1995. U.S.
economic growth, as measured by gross domestic product (GDP), rose 4.9 percent
in the third quarter of 2007, well above the 3.8 percent posted during the
second quarter. Despite the strong third-quarter GDP growth, the unemployment
rate rose slightly for the six-month period. High energy costs, volatile
financial markets and weak housing conditions all contributed to a decline in
consumer confidence during the period.

Financial markets grew increasingly volatile during the reporting period as the
fallout from the troubles in the subprime mortgage sector spread across the
broader fixed income and lending markets. Citing deteriorating financial market
conditions and the negative impact that tighter credit conditions could have in
restraining economic growth, the Federal Open Market Committee (the "Fed")
reduced its federal funds target rate 50 basis points in September, with
additional reductions of 25 basis points in both October and December. At its
December 11 meeting, the Fed noted that strains in financial markets increased
in recent weeks and that incoming data suggested economic growth was slowing. On
December 12, seeking to further improve credit market liquidity, the Fed
announced the creation of a Term Auction Facility (TAF) whereby term funds would
be auctioned to depository institutions against a wide variety of collateral.
TAF auctions are likely to continue for as long as credit market conditions
warrant.

PERFORMANCE ANALYSIS

As of December 31, 2007, Active Assets Institutional Government Securities Trust
had net assets of approximately $1.85 billion and an average portfolio maturity
of 35 days. For the six-month period ended December 31, 2007, the Fund provided
a total return of 2.49 percent. For the seven-day period ended December 31,
2007, the Fund provided an effective annualized yield of 4.38 percent and a
current yield of 4.29 percent, while its 30-day moving average yield for
December was 4.43 percent. Past performance is no guarantee of future results.

Our strategy in managing the Fund remained consistent with our long-term focus
on preservation of capital and liquidity. We attempt to manage the Fund
conservatively by purchasing high-quality Federal Agency obligations and
overnight repurchase agreements. In mid-to-late December, we took advantage of
year-end funding pressures and broker-dealer balance sheet constraints to
purchase two- and three-month discount notes. Due to substantial asset growth
experienced over the past six months, we maintained the Fund's weighted average
maturity shorter than usual.

There is no guarantee that any sectors mentioned will continue to perform as
discussed herein or that securities in such sectors will be held by the Fund in
the future.

<Table>
<Caption>
PORTFOLIO COMPOSITION

U.S. Government
Agencies -- Discount Notes 45.5%
U.S. Government
Agencies -- Floating Rate Notes 24.0
Repurchase Agreements 18.1
U.S. Government
Agencies -- Debenture Bonds 12.4
</Table>

<Table>
<Caption>
MATURITY SCHEDULE

1 - 30 Days 69.3%
31 - 60 Days 16.6
61 - 90 Days 6.4
91 - 120 Days 1.5
121+ Days 6.2
</Table>

Data as of December 31, 2007. Subject to change daily. All percentages for
portfolio composition and maturity schedule are as a percentage of total
investments. These data are provided for informational purposes only and should
not be deemed a recommendation to buy or sell the securities mentioned. Morgan
Stanley is a full-service securities firm engaged in securities trading and
brokerage activities, investment banking, research and analysis, financing and
financial advisory services.

INVESTMENT STRATEGY

THE FUND INVESTS AT LEAST 80 PERCENT OF ITS ASSETS IN HIGH QUALITY, SHORT-TERM
U.S. GOVERNMENT SECURITIES. IN SELECTING INVESTMENTS, THE FUND'S "INVESTMENT
ADVISER," MORGAN STANLEY INVESTMENT ADVISORS INC., SEEKS TO MAINTAIN THE FUND'S
SHARE PRICE AT $1.00. THE SHARE PRICE REMAINING STABLE AT $1.00 MEANS THAT THE
FUND WOULD PRESERVE THE PRINCIPAL VALUE OF YOUR INVESTMENT.

AN INVESTMENT IN THE FUND IS NOT INSURED OR GUARANTEED BY THE FEDERAL DEPOSIT
INSURANCE CORPORATION OR ANY OTHER GOVERNMENT AGENCY. ALTHOUGH THE FUND SEEKS TO
PRESERVE THE VALUE OF YOUR INVESTMENT AT $1.00 PER SHARE, IT IS POSSIBLE TO LOSE
MONEY BY INVESTING IN THE FUND.

FOR MORE INFORMATION ABOUT PORTFOLIO HOLDINGS

EACH MORGAN STANLEY FUND PROVIDES A COMPLETE SCHEDULE OF PORTFOLIO HOLDINGS IN
ITS SEMIANNUAL AND ANNUAL REPORTS WITHIN 60 DAYS OF THE END OF THE FUND'S SECOND
AND FOURTH FISCAL QUARTERS. THE SEMIANNUAL REPORTS AND THE ANNUAL REPORTS ARE
FILED ELECTRONICALLY WITH THE SECURITIES AND EXCHANGE COMMISSION (SEC) ON FORM
N-CSRS AND FORM N-CSR, RESPECTIVELY. MORGAN STANLEY ALSO DELIVERS THE SEMIANNUAL
AND ANNUAL REPORTS TO FUND SHAREHOLDERS AND MAKES THESE REPORTS AVAILABLE ON ITS
PUBLIC WEB SITE, WWW.MORGANSTANLEY.COM. EACH MORGAN STANLEY FUND ALSO FILES A
COMPLETE SCHEDULE OF PORTFOLIO HOLDINGS WITH THE SEC FOR THE FUND'S FIRST AND
THIRD FISCAL QUARTERS ON FORM N-Q. MORGAN STANLEY DOES NOT DELIVER THE REPORTS
FOR THE FIRST AND THIRD FISCAL QUARTERS TO SHAREHOLDERS, NOR ARE THE REPORTS
POSTED TO THE MORGAN STANLEY PUBLIC WEB SITE. YOU MAY, HOWEVER, OBTAIN THE FORM
N-Q FILINGS (AS WELL AS THE FORM N-CSR AND N-CSRS FILINGS) BY ACCESSING THE
SEC'S WEB SITE, HTTP://WWW.SEC.GOV. YOU MAY ALSO REVIEW AND COPY

THEM AT THE SEC'S PUBLIC REFERENCE ROOM IN WASHINGTON, DC. INFORMATION ON THE
OPERATION OF THE SEC'S PUBLIC REFERENCE ROOM MAY BE OBTAINED BY CALLING THE SEC
AT (800) SEC-0330. YOU CAN ALSO REQUEST COPIES OF THESE MATERIALS, UPON PAYMENT
OF A DUPLICATING FEE, BY ELECTRONIC REQUEST AT THE SEC'S E-MAIL ADDRESS
(PUBLICINFO@SEC.GOV) OR BY WRITING THE PUBLIC REFERENCE SECTION OF THE SEC,
WASHINGTON, DC 20549-0102.

HOUSEHOLDING NOTICE

TO REDUCE PRINTING AND MAILING COSTS, THE FUND ATTEMPTS TO ELIMINATE DUPLICATE
MAILINGS TO THE SAME ADDRESS. THE FUND DELIVERS A SINGLE COPY OF CERTAIN
SHAREHOLDER DOCUMENTS, INCLUDING SHAREHOLDER REPORTS, PROSPECTUSES AND PROXY
MATERIALS, TO INVESTORS WITH THE SAME LAST NAME WHO RESIDE AT THE SAME ADDRESS.
YOUR PARTICIPATION IN THIS PROGRAM WILL CONTINUE FOR AN UNLIMITED PERIOD OF TIME
UNLESS YOU INSTRUCT US OTHERWISE. YOU CAN REQUEST MULTIPLE COPIES OF THESE
DOCUMENTS BY CALLING (800) 869-NEWS, 8:00 A.M. TO 8:00 P.M., ET. ONCE OUR
CUSTOMER SERVICE CENTER HAS RECEIVED YOUR INSTRUCTIONS, WE WILL BEGIN SENDING
INDIVIDUAL COPIES FOR EACH ACCOUNT WITHIN 30 DAYS.

EXPENSE EXAMPLE

As a shareholder of the Fund, you incur ongoing costs, including advisory fees
and other Fund expenses. This example is intended to help you understand your
ongoing costs (in dollars) of investing in the Fund and to compare these costs
with the ongoing costs of investing in other mutual funds.

The example is based on an investment of $1,000 invested at the beginning of the
period and held for the entire period 07/01/07 - 12/31/07.

ACTUAL EXPENSES

The first line of the table below provides information about actual account
values and actual expenses. You may use the information in this line, together
with the amount you invested, to estimate the expenses that you paid over the
period. Simply divide your account value by $1,000 (for example, an $8,600
account value divided by $1,000 = 8.6), then multiply the result by the number
in the first line under the heading entitled "Expenses Paid During Period" to
estimate the expenses you paid on your account during this period.

HYPOTHETICAL EXAMPLE FOR COMPARISON PURPOSES

The second line of the table below provides information about hypothetical
expenses based on the Fund's actual expense ratio and an assumed rate of return
of 5% per year before expenses, which is not the Fund's actual return. The
hypothetical account values and expenses may not be used to estimate the actual
ending account balance or expenses you paid for the period. You may use this
information to compare the ongoing cost of investing in the Fund and other
funds. To do so, compare this 5% hypothetical example with the 5% hypothetical
examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the table are meant to highlight your
ongoing costs only. Therefore, the second line of the table is useful in
comparing ongoing costs, and will not help you determine the relative total cost
of owning different funds that have transactional costs, such as sales charges
(loads), and redemption fees, or exchange fees.

<Table>
<Caption>
BEGINNING ENDING EXPENSES PAID
ACCOUNT VALUE ACCOUNT VALUE DURING PERIOD*
------------- ------------- --------------
07/01/07 -
07/01/07 12/31/07 12/31/07
------------- ------------- --------------

Actual (2.49% return).......................... $1,000.00 $1,024.90 $0.92
Hypothetical (5% annual return before
expenses).................................... $1,000.00 $1,024.30 $0.92
</Table>

- ---------
* Expenses are equal to the Fund's annualized expense ratio of 0.18%
multiplied by the average account value over the period, multiplied by
184/365 (to reflect the one-half year period).

Active Assets Institutional Government Securities Trust
PORTFOLIO OF INVESTMENTS - DECEMBER 31, 2007 (UNAUDITED)

<Table>
<Caption>
ANNUALIZED
PRINCIPAL YIELD
AMOUNT IN ON DATE OF MATURITY
THOUSANDS DESCRIPTION PURCHASE DATES VALUE
- ------------------------------------------------------------------------------------------------

U.S. Government Agencies - Discount Notes (45.4%)
$832,226 Federal Home Loan Banks......... 3.15 - 5.07% 01/02/08 - 03/19/08 $831,424,876
7,845 Federal National Mortgage
Assoc. ....................... 4.30 03/12/2008 7,780,017
------------
Total U.S. Government Agencies - Discount Notes (Cost $839,204,893).. 839,204,893
------------
U.S. Government Agencies - Floating Rate Notes (23.9%)
113,750 Federal Farm Credit Banks....... 4.24 - 4.90+ 01/02/08 - 11/14/08* 113,745,265
278,900 Federal Home Loan Banks......... 4.22 - 5.12+ 01/02/08 - 02/28/08* 278,947,674
50,000 Freddie Mac..................... 4.67+ 03/30/2008* 49,983,759
------------
Total U.S. Government Agencies - Floating Rate Notes (Cost
$442,676,698)......................................................... 442,676,698
------------
Repurchase Agreements (18.0%)
202,650 BNP Paribas (dated 12/31/07;
proceeds $202,700,663) (a).... 4.50 01/02/08 202,650,000
30,000 BNP Paribas (dated 12/26/07;
proceeds $30,026,833) (b)..... 4.60 01/02/08 30,000,000
20,000 BNP Paribas (dated 12/27/07;
proceeds $20,019,444) (c)..... 5.00 01/03/08 20,000,000
20,000 BNP Paribas (dated 12/12/07;
proceeds $20,057,500) (d)..... 4.50 01/04/08 20,000,000
20,000 BNP Paribas (dated 12/11/07;
proceeds $20,078,667) (e)..... 4.72 01/10/08 20,000,000
10,000 Barclays Capital Inc. (dated
07/18/07; proceeds
$10,393,811) (f).............. 5.29 04/11/08 10,000,000
10,000 Deutsche Bank Securities LLC
(dated 11/29/07; proceeds
$10,044,861) (g).............. 4.75 01/02/08 10,000,000
10,000 Deutsche Bank Securities LLC
(dated 10/15/07; proceeds
$10,116,600) (g).............. 4.77 01/11/08 10,000,000
10,000 Deutsche Bank Securities LLC
(dated 12/13/07; proceeds
$10,073,333) (g).............. 4.40 02/11/08 10,000,000
------------
Total Repurchase Agreements (Cost $332,650,000)....................... 332,650,000
------------
U.S. Government Agencies - Debenture Bonds (12.4%)
6,055 Federal Farm Credit Banks....... 4.62 - 5.12 01/28/08 - 10/16/08 6,053,927
222,315 Federal Home Loan Banks......... 4.18 - 5.19 01/15/08 - 12/12/08 222,304,316
------------

</Table>

<Table>

Total U.S. Government Agencies - Debenture Bonds (Cost
$228,358,243)................................................. 228,358,243
--------------
Total Investments (Cost $1,842,889,834) (h)........... 99.7% 1,842,889,834

Other Assets in Excess of Liabilities................. 0.3 6,071,033
----- --------------
Net Assets............................................ 100.0% $1,848,960,867
===== ==============

</Table>

See Notes to Financial Statements

Active Assets Institutional Government Securities Trust
PORTFOLIO OF INVESTMENTS - DECEMBER 31, 2007 (UNAUDITED) continued

- ----------

<Table>

+ Rate shown is the rate in effect at December 31, 2007.
* Date of next interest rate reset.
(a) Collateralized by Federal National Mortgage Assoc. 6.00% due
10/01/37 valued at $206,703,001.
(b) Collateralized by Federal National Mortgage Assoc. 6.00% due
11/01/37 - 12/01/37 valued at $30,600,001.
(c) Collateralized by Federal National Mortgage Assoc. 6.00% due
11/01/37 valued at $20,400,001.
(d) Collateralized by Federal National Mortgage Assoc. 6.00% due
11/01/37 valued at $20,400,001.
(e) Collateralized by Federal National Mortgage Assoc. 6.00% due
11/01/37 valued at $20,400,001.
(f) Collateralized by Freddie Mac 6.00% due 01/12/22 valued at
$10,200,358.
(g) Collateralized by Freddie Mac 5.00% - 6.50% due 11/01/35 - 11/01/37
valued at $30,600,000.
(h) Cost is the same for federal income tax purposes.
</Table>

See Notes to Financial Statements

Active Assets Institutional Government Securities Trust
FINANCIAL STATEMENTS

Statement of Assets and Liabilities
December 31, 2007 (unaudited)

<Table>

Assets:
Investments in securities, at value
(cost $1,842,889,834) (including repurchase agreements of
$332,650,000)............................................... $1,842,889,834
Cash.......................................................... 644,857
Interest receivable........................................... 6,045,591
Prepaid expenses and other assets............................. 66,752
--------------
Total Assets............................................... 1,849,647,034
--------------
Liabilities:
Payable for:
Dividends to shareholders.................................. 405,527
Investment advisory fee.................................... 123,053
Administration fee......................................... 61,527
Accrued expenses and other payables........................... 96,060
--------------
Total Liabilities.......................................... 686,167
--------------
Net Assets................................................. $1,848,960,867
==============
Composition of Net Assets:
Paid-in-capital............................................... $1,848,964,695
Accumulated undistributed net investment income............... 6,718
Net realized loss............................................. (10,546)
--------------
Net Assets................................................. $1,848,960,867
==============
Net Asset Value Per Share
1,848,978,045 shares outstanding (unlimited shares authorized
of $.01 par value).......................................... $1.00
=====

</Table>

See Notes to Financial Statements

Active Assets Institutional Government Securities Trust
FINANCIAL STATEMENTS continued

Statement of Operations
For the six months ended December 31, 2007 (unaudited)

<Table>

Net Investment Income:
Interest Income................................................. $32,215,441
-----------
Expenses
Investment advisory fee......................................... 637,075
Administration fee.............................................. 318,538
Registration fees............................................... 75,986
Professional fees............................................... 37,734
Custodian fees.................................................. 34,302
Shareholder reports and notices................................. 19,437
Trustees' fees and expenses..................................... 5,695
Transfer agent fees and expenses................................ 1,508
Other........................................................... 32,455
-----------
Total Expenses............................................... 1,162,730
Less: expense offset............................................ (10)
-----------
Net Expenses................................................. 1,162,720
-----------
Net Investment Income........................................ 31,052,721
Net Realized Loss............................................ (10,546)
-----------
Net Increase.................................................... $31,042,175
===========

</Table>

See Notes to Financial Statements

Active Assets Institutional Government Securities Trust
FINANCIAL STATEMENTS continued

Statements of Changes in Net Assets

<Table>
<Caption>
FOR THE SIX FOR THE YEAR
MONTHS ENDED ENDED
DECEMBER 31, 2007 JUNE 30, 2007
----------------- --------------
(unaudited)

Increase (Decrease) in Net Assets:
Operations:
Net investment income............................. $ 31,052,721 $ 43,298,608
Net realized loss................................. (10,546) --
-------------- --------------
Net Increase................................... 31,042,175 43,298,608
Dividends to shareholders from net investment
income.......................................... (31,059,353) (43,298,608)
Net increase from transactions in shares of
beneficial interest............................. 771,134,534 409,679,955
-------------- --------------
Net Increase................................... 771,117,356 409,679,955
Net Assets:
Beginning of period............................... 1,077,843,511 668,163,556
-------------- --------------
End of Period
(Including accumulated undistributed net
investment income of $6,718 and $13,350,
respectively)..................................... $1,848,960,867 $1,077,843,511
============== ==============

</Table>

See Notes to Financial Statements

Active Assets Institutional Government Securities Trust
NOTES TO FINANCIAL STATEMENTS - DECEMBER 31, 2007 (UNAUDITED)

1. Organization and Accounting Policies
Active Assets Institutional Government Securities Trust (the "Fund") is
registered under the Investment Company Act of 1940, as amended (the "Act"), as
a diversified, open-end management investment company. The Fund's investment
objectives are high current income, preservation of capital and liquidity. The
Fund was organized as a Massachusetts business trust on January 18, 2002 and
commenced operations on November 4, 2002.

The following is a summary of significant accounting policies:

A. Valuation of Investments -- Portfolio securities are valued at amortized
cost, which approximates market value, in accordance with Rule 2a-7 under the
Act .

B. Accounting for Investments -- Security transactions are accounted for on the
trade date (date the order to buy or sell is executed). Realized gains and
losses on security transactions are determined by the identified cost method.
Discounts are accreted and premiums are amortized over the life of the
respective securities and are included in interest income. Interest income is
accrued daily.

C. Repurchase Agreements -- The Fund may invest directly with institutions in
repurchase agreements. The Fund's custodian receives the collateral, which is
marked-to-market daily to determine that the value of the collateral does not
decrease below the repurchase price plus accrued interest.

D. Federal Income Tax Policy -- It is the Fund's policy to comply with the
requirements of Subchapter M of the Internal Revenue Code applicable to
regulated investment companies and to distribute substantially all of its
taxable income to its shareholders. Therefore, no provision for federal income
taxes is required. The Fund files tax returns with the U.S. Internal Revenue
Service and New York. The Fund adopted the provisions of the Financial
Accounting Standards Board ("FASB") Interpretation No. 48 ("FIN 48") Accounting
for Uncertainty in Income Taxes on June 29, 2007. FIN 48 sets forth a minimum
threshold for financial statement recognition of the benefit of a tax position
taken or expected to be taken in a tax return. The implementation of FIN 48 did
not result in any unrecognized tax benefits in the accompanying financial
statements. If applicable, the Fund recognizes interest accrued related to
unrecognized tax benefits in interest expense and penalties in other expenses in
the Statement of Operations. Each of the tax years in the four year period ended
December 31, 2007, remains subject to examination by taxing authorities.

E. Dividends and Distributions to Shareholders -- The Fund records dividends and
distributions to shareholders as of the close of each business day.

Active Assets Institutional Government Securities Trust
NOTES TO FINANCIAL STATEMENTS - DECEMBER 31, 2007 (UNAUDITED) continued

F. Use of Estimates -- The preparation of financial statements in accordance
with generally accepted accounting principles requires management to make
estimates and assumptions that affect the reported amounts and disclosures.
Actual results could differ from those estimates.

2. Investment Advisory/Administration Agreements
Pursuant to an Investment Advisory Agreement with Morgan Stanley Investment
Advisors Inc. (the "Investment Adviser"), the Fund pays the Investment Adviser
an advisory fee, accrued daily and payable monthly, by applying the annual rate
of 0.10% to the net assets of the Fund determined as of the close of each
business day.

Pursuant to an Administration Agreement with Morgan Stanley Services Company
Inc. (the "Administrator"), an affiliate of the Investment Adviser, the Fund
pays an administration fee, accrued daily and payable monthly, by applying the
annual rate of 0.05% to the Fund's daily net assets.

Under an agreement between the Administrator and State Street Bank and Trust
Company ("State Street"), State Street provides certain administrative services
to the Fund. For such services, the Administrator pays State Street a portion of
the fee the Administrator receives from the Fund.

The Investment Adviser and Administrator have agreed to assume the Fund's
operating expenses (except for brokerage fees) through June 30, 2008, to the
extent that such expenses exceed on an annualized basis, 0.20% of the average
daily net assets.

3. Security Transactions and Transactions with Affiliates
The cost of purchases and proceeds from sales/maturities of portfolio securities
for the six months ended December 31, 2007, aggregated $60,575,951,129 and
$59,813,265,000, respectively.

Morgan Stanley Trust, an affiliate of the Investment Adviser and Administrator,
is the Fund's transfer agent.

The Fund has an unfunded Deferred Compensation Plan (the "Compensation Plan")
which allows each independent Trustee to defer payment of all, or a portion, of
the fees he or she receives for serving on the Board of Trustees. Each eligible
Trustee generally may elect to have the deferred amounts credited with a return
equal to the total return on one or more of the Morgan Stanley funds that are
offered as investment options under the Compensation Plan.
Appreciation/depreciation and distributions received from these investments are
recorded with an offsetting increase/decrease in the deferred compensation
obligation and do not affect the net asset value of the Fund.

Active Assets Institutional Government Securities Trust
NOTES TO FINANCIAL STATEMENTS - DECEMBER 31, 2007 (UNAUDITED) continued

4. Expense Offset
The expense offset represents a reduction of the fees and expenses for interest
earned on cash balances maintained by the Fund with the transfer agent.

5. Shares of Beneficial Interest
Transactions in shares of beneficial interest, at $1.00 per share, were as
follows:

<Table>
<Caption>
FOR THE SIX FOR THE YEAR
MONTHS ENDED ENDED
DECEMBER 31, 2007 JUNE 30, 2007
----------------- --------------
(unaudited)

Shares sold...................................... 5,015,855,472 3,748,729,942
Shares issued in reinvestment of dividends....... 30,875,352 43,059,829
-------------- --------------
5,046,730,824 3,791,789,771
Shares redeemed.................................. (4,275,596,290) (3,382,109,816)
-------------- --------------
Net increase in shares outstanding............... 771,134,534 409,679,955
============== ==============

</Table>

6. Accounting Pronouncement
In September 2006, Statement of Financial Accounting Standards No. 157, Fair
Value Measurements (SFAS 157), was issued and is effective for fiscal years
beginning after November 15, 2007. SFAS 157 defines fair value, establishes a
framework for measuring fair value and expands disclosures about fair value
measurements. Management is currently evaluating the impact the adoption of SFAS
157 will have on the Fund's financial statement disclosures.

Active Assets Institutional Government Securities Trust
FINANCIAL HIGHLIGHTS

Selected ratios and per share data for a share of beneficial interest
outstanding throughout each period:

<Table>
<Caption>
FOR THE SIX FOR THE YEAR ENDED JUNE 30,
MONTHS ENDED ----------------------------------------------------
DECEMBER 31, 2007 2007 2006 2005 2004
----------------- ---------- -------- -------- --------
(unaudited)

Selected Per Share Data:

Net asset value, beginning of period......... $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00
------ ------ ------ ------ ------

Net income from investment operations........ 0.025 0.051 0.041 0.021 0.010

Less dividends from net investment income.... (0.025) (0.051) (0.041) (0.021) (0.010)+
------- ------- ------- ------- -------

Net asset value, end of period............... $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00
====== ====== ====== ====== ======

Total Return................................. 2.49%(1) 5.22% 4.15% 2.12% 0.97%

Ratios to Average Net Assets:
Total expenses (before expense offset)....... 0.18%(2) 0.19% 0.15%(3) 0.10%(3) 0.09%(3)

Net investment income........................ 4.87%(2) 5.10% 4.11%(3) 2.15%(3) 0.96%(3)

Supplemental Data:
Net assets, end of period, in thousands...... $1,848,961 $1,077,844 $668,164 $473,818 $385,845
<Caption>
FOR THE PERIOD
NOVEMBER 4, 2002*
THROUGH
JUNE 30, 2003
-----------------

Selected Per Share Data:

Net asset value, beginning of period......... $ 1.00
------

Net income from investment operations........ 0.008

Less dividends from net investment income.... (0.008)
-------

Net asset value, end of period............... $ 1.00
======

Total Return................................. 0.82%(1)

Ratios to Average Net Assets:
Total expenses (before expense offset)....... 0.03%(2)(3)

Net investment income........................ 1.17%(2)(3)

Supplemental Data:
Net assets, end of period, in thousands...... $155,363
</Table>

- ----------

<Table>

* Commencement of operations.
+ Includes capital gain distribution of less than $0.001.
(1) Not annualized.
(2) Annualized.
(3) If the Fund had borne all of its expenses that were reimbursed or waived
by the Investment Adviser and Administrator, the annualized expense and
net investment income ratios, before expense offset, would have been as
follows:
</Table>

<Table>
<Caption>
EXPENSE NET INVESTMENT
PERIOD ENDED: RATIO INCOME RATIO
- ------------- ------- --------------

June 30, 2006 0.20% 4.06%
June 30, 2005 0.20 2.05
June 30, 2004 0.21 0.84
June 30, 2003 0.47 0.73
</Table>

See Notes to Financial Statements

(This Page Intentionally Left Blank)

TRUSTEES

Michael Bozic
James F. Higgins
Dr. Manuel H. Johnson
Joseph J. Kearns
Michael E. Nugent
Fergus Reid

OFFICERS

Michael E. Nugent
Chairperson of the Board

Ronald E. Robison
President and Principal Executive Officer

J. David Germany
Vice President

Dennis F. Shea
Vice President

Amy R. Doberman
Vice President

Carsten Otto
Chief Compliance Officer

Stefanie V. Chang Yu
Vice President

Francis J. Smith
Treasurer and Chief Financial Officer

Mary E. Mullin
Secretary

TRANSFER AGENT

Morgan Stanley Trust
Harborside Financial Center, Plaza Two
Jersey City, New Jersey 07311

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Deloitte & Touche LLP
Two World Financial Center
New York, New York 10281

LEGAL COUNSEL

Clifford Chance US LLP
31 West 52nd Street
New York, New York 10019

COUNSEL TO THE INDEPENDENT TRUSTEES

Kramer Levin Naftalis & Frankel LLP
1177 Avenue of the Americas
New York, New York 10036

INVESTMENT ADVISER

Morgan Stanley Investment Advisors Inc.
522 Fifth Avenue
New York, New York 10036

The financial statements included herein have been taken from the records of the
Fund without examination by the independent auditors and accordingly they do not
express an opinion thereon.

This report is submitted for the general information of the shareholders of the
Fund. For more detailed information about the Fund, its fees and expenses and
other pertinent information, please read its Prospectus. The Fund's Statement of
Additional Information contains additional information about the Fund, including
its trustees. It is available, without charge, by calling (800) 869-NEWS.

This report is not authorized for distribution to prospective investors in the
Fund unless preceded or accompanied by an effective Prospectus. Read the
Prospectus carefully before investing.

[MORGAN STANLEY LOGO]

MORGAN STANLEY FUNDS

Active Assets
Institutional
Government
Securities Trust

Semiannual Report
December 31, 2007

AISSAN
IU08-00804P-Y12/07

Item 2. Code of Ethics.

Not applicable for semiannual reports.

Item 3. Audit Committee Financial Expert.

Not applicable for semiannual reports.

Item 4. Principal Accountant Fees and Services

Not applicable for semiannual reports.

Item 5. Audit Committee of Listed Registrants.

Not applicable for semiannual reports.

Item 6.

Refer to Item 1.

Item 7. Disclosure of Proxy Voting Policies and Procedures for Closed-End
Management Investment Companies.

Not applicable for semiannual reports.

Item 8. Portfolio Managers of Closed-End Management Investment Companies

Applicable only to reports filed by closed-end funds.

Item 9. Closed-End Fund Repurchases

Applicable to reports filed by closed-end funds.

Item 10. Submission of Matters to a Vote of Security Holders

Not applicable.

Item 11. Controls and Procedures

(a) The Fund's principal executive officer and principal financial officer have
concluded that the Fund's disclosure controls and procedures are sufficient to
ensure that information required to be disclosed by the Fund in this Form N-CSR
was recorded, processed, summarized and reported within the time periods
specified in the Securities and Exchange Commission's rules and forms, based
upon such officers' evaluation of these controls and procedures as of a date
within 90 days of the filing date of the report.

(b) There were no changes in the registrant's internal control over financial
reporting that occurred during the second fiscal quarter of the period covered
by this report that has materially affected, or is reasonably likely to
materially affect, the registrant's internal control over financial reporting.

Item 12. Exhibits

(a) Code of Ethics - Not applicable for semiannual reports.

(b) A separate certification for each principal executive officer and principal
financial officer of the registrant are attached hereto as part of EX-99.CERT.

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.

Active Assets Institutional Government Securities Trust

/s/ Ronald E. Robison
Ronald E. Robison
Principal Executive Officer
February 15, 2008

Pursuant to the requirements of the Securities Exchange Act of 1934 and the
Investment Company Act of 1940, this report has been signed by the following
persons on behalf of the registrant and in the capacities and on the dates
indicated.

/s/ Ronald E. Robison
Ronald E. Robison
Principal Executive Officer
February 15, 2008

/s/ Francis Smith
Francis Smith
Principal Financial Officer
February 15, 2008