UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                       ----------------------------------

                                    FORM 11-K

(Mark One)

[X]               Annual report pursuant to Section 15(d) of the
                        Securities Exchange Act of 1934

                   For the fiscal year ended December 31, 2005

                                       OR

[ ]              Transition report pursuant to Section 15(d)
                     of the Securities Exchange Act of 1934

                     For the transition period from to ____

Commission File Number 1-11377


CINERGY CORP. UNION EMPLOYEES' 401(k) PLAN./


                         CINERGY CORP. UNION EMPLOYEES'
                                  401 (k) PLAN
                             139 East Fourth Street
                             Cincinnati, Ohio 45202


              (Full title of the Plan and the address of the Plan,
                if different from that of the issuer named below)

                                  CINERGY CORP.
                             139 East Fourth Street
                             Cincinnati, Ohio 45202

           (Name of issuer of the common stock issued pursuant to the
             Plan and the address of its principal executive office)





CINERGY CORP.
UNION EMPLOYEES' 401(k) PLAN

TABLE OF CONTENTS
- -----------------------------------------------------------------------------


                                                                        Page

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM                   1

FINANCIAL STATEMENTS:

   Statements of Net Assets Available for Benefits as of
     December 31, 2005 and 2004                                           2

   Statements of Changes in Net Assets Available for Benefits
     for the Years Ended December 31, 2005 and 2004                       3

   Notes to Financial Statements                                         4-10

SUPPLEMENTAL SCHEDULE--                                                   11

   Form 5500, Schedule H, Part IV, Line 4i--Schedule of Assets (Held at End of
     Year) as of December 31, 2005                                        12

   NOTE:    All other schedules required by Section 2520.103-10 of the
            Department of Labor's Rules and Regulations for Reporting and
            Disclosure under the Employee Retirement Income Security Act of 1974
            have been omitted because they are not applicable.

SIGNATURE                                                                 S-1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM                  E-1




REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM


To the Benefits Committee of Cinergy Corp.
Cincinnati, Ohio

We have audited the accompanying statements of net assets available for benefits
of the Cinergy Corp. Union Employees' 401(k) Plan (the "Plan") as of December
31, 2005 and 2004, and the related statements of changes in net assets available
for benefits for the years then ended. These financial statements are the
responsibility of the Plan's management. Our responsibility is to express an
opinion on these financial statements based on our audits.

We conducted our audits in accordance with standards of the Public Company
Accounting Oversight Board (United States). Those standards require that we plan
and perform the audit to obtain reasonable assurance about whether the financial
statements are free of material misstatement. The plan is not required to have,
nor were we engaged to perform, an audit of its internal control over financial
reporting. Our audits included consideration of internal control over financial
reporting as a basis for designing audit procedures that are appropriate in the
circumstances, but not for the purpose of expressing an opinion on the
effectiveness of the Plan's internal control over financial reporting.
Accordingly, we express no such opinion. An audit also includes examining, on a
test basis, evidence supporting the amounts and disclosures in the financial
statements, assessing the accounting principles used and significant estimates
made by management, as well as evaluating the overall financial statement
presentation. We believe that our audits provide a reasonable basis for our
opinion.

In our opinion, such financial statements present fairly, in all material
respects, the net assets available for benefits of the Plan as of December 31,
2005 and 2004, and the changes in net assets available for benefits for the
years then ended in conformity with accounting principles generally accepted in
the United States of America.

Our audits were conducted for the purpose of forming an opinion on the basic
financial statements taken as a whole. The supplemental schedule of assets (held
at end of year) as of December 31, 2005 is presented for the purpose of
additional analysis and is not a required part of the basic financial
statements, but is supplementary information required by the Department of
Labor's Rules and Regulations for Reporting and Disclosure under the Employee
Retirement Income Security Act of 1974. This schedule is the responsibility of
the Plan's management. Such schedule has been subjected to the auditing
procedures applied in our audit of the basic 2005 financial statements and, in
our opinion, is fairly stated in all material respects when considered in
relation to the basic financial statements taken as a whole.



Cincinnati, Ohio
June 23, 2006





CINERGY CORP.
UNION EMPLOYEES' 401(k) PLAN

STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS
DECEMBER 31, 2005 AND 2004
- ----------------------------------------------------------------------------


ASSETS                                           2005                 2004

CURRENT ASSETS:
  Investments--at fair value (see Notes 3 and 4):
    Plan interest in Cinergy Corp. Common
     Stock Master Trust                    $  59,234,427         $  56,024,465
    Mutual funds                              79,592,458            71,435,003
    Interest bearing cash                      9,985,945             9,987,145
    Common/collective trust                    2,191,099             1,491,772
    Loans to participants                      4,602,558             4,889,917
                                          ---------------       ---------------

           Total investments                 155,606,487           143,828,302

  Employer's contribution receivable             847,037               467,687
                                         ----------------      ----------------

NET ASSETS AVAILABLE FOR BENEFITS           $156,453,524          $144,295,989
                                            ============          ============


See notes to financial statements.





CINERGY CORP.
UNION EMPLOYEES' 401(k) PLAN

STATEMENTS OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS
YEARS ENDED DECEMBER 31, 2005 AND 2004
- ---------------------------------------------------------------------------


                                                  2005                 2004

ADDITIONS--
  Additions to net assets attributed to:
    Investment income:
      Plan interest in Cinergy Corp. Common
        Stock Master Trust (see Note 4)    $    3,983,898       $     6,427,198
      Net appreciation in fair value of
        investments                             2,239,878             4,693,716
      Interest and dividends                    3,537,140             2,036,466
      Participant loan interest income            259,517               258,055
                                              --------------         ----------

           Net investment income               10,020,433            13,415,435
                                              --------------         ----------

    Contributions:
      Participant                               6,963,066             6,605,398
      Employer                                  3,750,783             3,336,708
      Rollover                                    156,976                29,242
                                              --------------         ----------

           Total contributions                 10,870,825             9,971,348

           Total additions                     20,891,258            23,386,783
                                              --------------         ----------

DEDUCTIONS:
  Deductions from net assets attributed to:
    Benefits paid to participants              (7,596,613)          (5,417,311)
    Dividends paid in cash                        (67,384)             (57,836)
    Deemed distribution of loans to participants   (2,027)
    Administration fees                           (20,447)             (22,596)
                                              --------------         ----------

           Total deductions                    (7,686,471)          (5,497,743)

  Net increase prior to transfers              13,204,787            17,889,040
  Interplan transfers (see Note 2)             (1,047,252)            (955,034)
                                              --------------         ----------

                                                12,157,535           16,934,006

NET ASSETS AVAILABLE FOR BENEFITS:
  Beginning of year                            144,295,989          127,361,983
                                              ---------------        ----------

  End of year                                 $156,453,524         $144,295,989
                                             ================      ============


See notes to financial statements.






CINERGY CORP.
UNION EMPLOYEES' 401(K)PLAN

NOTES TO FINANCIAL STATEMENTS
DECEMBER 31, 2005 AND 2004
- ---------------------------------------------------------------------------


1.    PLAN DESCRIPTION

      The following description of the Cinergy Corp. Union Employees' 401(k)
      Plan (the "Plan") provides only general information. Participants should
      refer to the Plan Document for a more complete description of the Plan's
      provisions.

      General--The Plan is a defined contribution plan covering union employees
      of Cinergy Corp.'s subsidiaries (collectively, the "Company") represented
      by the International Brotherhood of Electrical Workers, Local 1393. The
      Plan is administered by the Cinergy Benefits Committee and trusteed by the
      Fidelity Management Trust Company ("Fidelity") and U.S. Trust Company of
      California N.A. ("US Trust"). The Plan is subject to the provisions of the
      Employee Retirement Income Security Act of 1974 ("ERISA"), as amended. A
      portion of the administrative expenses of the Plan are paid by the
      Company.

      Contributions--The Company automatically enrolls new full time employees
      eligible for the Plan at a 3% deferral rate. The contributions made to the
      plan on the employee's behalf will be invested in one or more funds
      selected in accordance with procedures established by the plan
      administrator. If an employee chooses not to participate, Fidelity, the
      recordkeeper, must be contacted by the employee to change the deferral
      rate to 0%.

      Under the Plan, the pre-tax contribution limit is 50% of annual base
      compensation up to the IRS maximum each year. In addition, a participant
      may make after-tax contributions up to 15% of annual base compensation.
      Pre-tax and after-tax contributions are subject to certain limitations.
      The pre-tax and after-tax contributions are invested by the trustee, as
      directed by each participant, in one or more investment funds, including
      the Cinergy Corp. Common Stock Master Trust.

      The Company matches 100% of the first 3% of pre-tax contributions from
      base pay plus 50% of the next 2% of pre-tax contributions from base pay.
      An additional incentive match will be a maximum of 1% of base pay based
      upon meeting corporate goals. Only employees making pre-tax contributions
      will receive the incentive match. All employer contributions are invested
      by the trustee in the Cinergy Corp. Common Stock Master Trust.

      The Company, at its discretion can make a profit sharing contribution to
      the Plan to eligible employees for the plan year in an amount determined
      by the Company. In 2005 and 2004, the amount of the Deferred Profit
      Sharing contribution was $305,168 and $122,296, respectively.

      Participants who are age 50 or older by the end of the year, may
      contribute an additional pre-tax amount over and above the IRS limits each
      year. For 2005 and 2004, the IRS allowed participants over the age of 50
      to contribute up to an additional $4,000 and $3,000 over and above the
      $14,000 and $13,000 pre-tax limit, respectively. Cinergy will not provide
      a base company match or incentive match on these additional contributions.

      Vesting--Participants are immediately vested in all contributions and
      earnings thereon, with the exception of Deferred Profit Sharing
      Contributions made by the Company which are vested after three years of
      service. However, the dividends on the Cinergy Corp. common stock on
      Deferred Profit Sharing Contributions are vested immediately.

      Participant Account--Each participant's account is credited with the
      participant's contribution and allocation of the Company's contribution
      and plan earnings. Allocations are based on the participant's account
      balance or contribution percentage as defined in the plan document. The
      benefit to which a participant is entitled is the benefit that can be
      provided from the participant's vested account.

      A participant may elect to change investment funds and/or the contribution
      allocation percentage among funds at any time.

      Payment of Benefits--Participants are generally eligible to receive
      distributions of assets from the Plan upon termination of employment
      including retirement, death, or disability. Distributions are paid in a
      lump sum for vested benefits of $1,000 or less. Distributions are paid in
      a lump sum or up to ten annual installments (at the election of the
      participant) for vested benefits greater than $1,000. Active participants
      are also eligible to apply to the Plan administrator for "hardship"
      withdrawals from their pretax account in accordance with Plan provisions.

      Participant Loans--Subject to certain limitations, participants may apply
      for loans from their pre-tax account balances. Interest on the loans is
      set at the prime rate plus 1% at the time of borrowing, and the loans are
      secured by the balance in the participant's account. Loans are to be
      repaid within 54 months through regular payroll deductions.

2.    SIGNIFICANT ACCOUNTING POLICIES

      Basis of Accounting--The accompanying financial statements of the Plan are
      prepared on an accrual basis.

      Investment Valuation and Income Recognition--Investments are stated at
      fair value. Shares of registered investment companies are valued at quoted
      redemption prices which represent the net asset value of shares held by
      the Plan at year-end. Cinergy common stock is valued at its quoted market
      price. Participant loans are valued at cost, which approximates fair
      value.

      Purchases and sales of securities are recorded on a trade-date basis.
      Interest income is recorded on the accrual basis. Dividends are recorded
      on the ex-dividend date.

      Transfers of assets between the Plan, the Cinergy Corp. Non-Union
      Employees' 401(k) Plan and the Cinergy Corp. Union Employees' Savings
      Incentive Plan occur as a result of changes in employee status between the
      union classification and the exempt and non-exempt classifications. Such
      transfers are reflected as interplan transfers on the statement of changes
      in net assets available for benefits.

      Use of Estimates--The preparation of financial statements in conformity
      with accounting principles generally accepted in the United States
      requires management to make estimates and assumptions that affect the
      reported amounts of assets and liabilities and changes therein, and
      disclosure of contingent assets and liabilities at the date of the
      financial statements. Actual results could differ from those estimates.

      Payments of Benefits--Benefit payments are recorded when paid.

3.    NON-PARTICIPANT DIRECTED INVESTMENTS

      Effective October 1, 2005, the Plan was amended to allow participants to
      transfer funds from the Cinergy Common Stock Master Trust to other
      investments options at any time. Therefore, all investments became
      participant directed. Information about the net assets and the significant
      components of the changes in net assets relating to non-participant
      directed balances in 2004 is as follows:

                                                                 December 31,
                                                                     2004

         Net assets--Cinergy Corp. Common Stock Master Trust      $  43,503,782
                                                                  =============


                                                                   Year Ended
                                                                   December 31,
                                                                      2004

         Changes in net assets:
           Employer contributions                                 $   3,335,591
           Dividends                                                  1,892,191
           Net appreciation                                           2,955,180
           Benefits paid to participants                            (1,124,087)
           Transfers to participant directed investments            (2,425,458)
           Interplan transfers                                        (471,750)
                                                                 --------------

                                                                  $   4,161,667




4.    INVESTMENTS

      The Plan invests in Cinergy Corp. Common Stock Master Trust which was
      established by the Company for certain of the Plans' sponsor's defined
      contribution 401(k) plans. Cinergy Corp. also sponsors the following
      plans, whose investments are held in the Master Trust described above:

             The Cinergy Corp. Union Employees' Savings Incentive Plan, which
             covers union employees of Cinergy Corp. and subsidiaries
             represented by The Utility Workers Union, Local 600, The
             International Brotherhood of Electrical Workers, Local 1347, The
             United Steelworkers of America, Local 12049 and Local 14214, The
             Paper, Allied-Industrial, Chemical and Energy Workers, Local 4-1,
             Unite, Local 2024 and Unite, Local 1093.

             The Cinergy Corp. Non-Union Employees' 401(k) Plan, which covers
             non-union employees' of Cinergy Corp. and subsidiaries who
             meet minimum age requirements.

      The Plan has an undivided interest in the Master Trust. Fidelity
      Management Trust Company in the name of US Trust as Trustee holds the Plan
      interest in Cinergy Corp. Common Stock Master Trust. A summary of the net
      assets of the Master Trusts as of December 31, 2005 and 2004 is as
      follows:


                                                      2005             2004

         Cash and cash equivalents              $    3,421,124   $    4,823,702
         Cinergy Corp. common stock                462,775,838      428,963,584
                                                 -------------    -------------


                                                      2005             2004

                    Total investments            466,196,962        433,787,286

         Receivables:

           Accrued interest                           11,810              6,532

           Securities sold                         1,705,296             41,713
                                                 -------------     ------------

                    Total assets                 467,914,068        433,835,531


         Liabilities--securities purchased         (109,812)           (64,030)
                                                 --------------    ------------

         Net assets of Cinergy Corp.
         Common Stock Master Trust              $467,804,256       $433,771,501
                                                ============       ============



Allocations of the Plan interest in Cinergy Corp. Common Stock Master Trust to
participating plans as of December 31 are as follows:

                                         2005                    2004
                                   Amount     Percent     Amount        Percent

Cinergy Corp. Union Employees' $  59,234,427    13%    $  56,024,465       13%
 401(k) Plan
Cinergy Corp. Non-Union
 Employees' 401(k) Plan          215,588,648    46       198,406,071       46
Cinergy Corp. Union Employees'
 Savings Incentive Plan          192,981,181    41       179,340,965       41
                               -------------    ---     -------------      ---

                                $467,804,256    100%    $433,771,501       100%
                                ============    ====    ============       ====


A summary of income of the Cinergy Corp. Common Stock Master Trust as of
December 31 is as follows:


                                                     2005              2004

       Cinergy Corp. Common Stock Master Trust:
         Interest and dividends                   $20,468,016      $19,381,810
         Net appreciation in fair value of
         investments                               10,401,289       30,212,573
                                                  ------------     ------------

       Net Trust investment income                $30,869,305      $49,594,383
                                                  ===========      ===========



      The Plan's investments (excluding the Cinergy Corp. Common Stock Master
      Trust, which is detailed above), which includes gains and losses on
      investments bought and sold, as well as held during the year, appreciated
      in value as follows:

                                                     2005              2004

       Mutual funds                               $2,175,208        $4,612,873
       Common/collective trust                        64,670            80,843
                                               -------------     -------------

       Net appreciation in fair
       value of investments                       $2,239,878        $4,693,716
                                                  ==========        ==========



Allocations of income in Cinergy Corp. Common Stock Master Trust to
participating plans as of December 31 are as follows:

                                           2005                     2004
                                   Amount       Percent      Amount      Percent

Cinergy Corp. Union Employees'   $  3,983,898     13%     $  6,427,198     13%
 401(k) Plan
Cinergy Corp. Non-Union Employees'
 401(k) Plan                       14,140,073     46        22,881,831      46
Cinergy Corp. Union Employees'
 Savings Incentive Plan            12,745,334     41        20,285,354      41
                                  ------------   ----     -------------     ---

                                 $ 30,869,305    100%      $49,594,383     100%
                                 ============    ====     =============    ====



     The fair value of individual investments that represent 5% or more of the
     Plan's net assets available for benefits as of December 31 are as follows:

                                                    2004               2003

*Plan interest in Cinergy Corp.
 Common Stock Master Trust                     $ 59,234,427        $56,024,465
 JP Morgan Prime Money Market Instrument          9,985,945          9,987,145
*Fidelity Magellan Fund                          25,656,918         26,040,754
*Fidelity Equity Income Fund                     17,792,544         16,927,024
*Fidelity Low-Priced Stock Fund                   8,623,056          7,368,609

*Denotes party-in-interst.


5.    FEDERAL INCOME TAX STATUS

      The Internal Revenue Service has determined and informed the Plan by
      letter dated December 9, 2002, that the Plan and related trust are
      designed in accordance with applicable sections of the Internal Revenue
      Code ("IRC"). The Plan has been amended since receiving the determination
      letter. However, the Plan administrator believes the Plan is designed and
      is being operated in compliance with the applicable requirements of the
      IRC. Therefore, no provision for income taxes has been recorded in the
      accompanying financial statements.

6.    PLAN TERMINATION

      Although it has not expressed any intent to do so, the Company has the
      right under the Plan to discontinue its contributions at any time and to
      terminate the Plan subject to the provisions of ERISA. Any unvested
      amounts in the participant's account may be forfeited upon termination of
      the plan.

7.    RELATED PARTY TRANSACTIONS

      Certain Plan investments are shares of mutual funds managed by Fidelity.
      Fidelity is the Trustee for all Plan investments, except for the Plan's
      interest in Cinergy Corp. Common Stock Master Trust, as defined by the
      Plan and therefore, these transactions qualify as party-in-interest
      transactions. US Trust is the Trustee for the Plan's interest in Cinergy
      Corp. Common Stock Master Trust, which holds common stock of the Company
      as defined by the Plan and therefore, these transactions qualify as
      party-in-interest transactions.

8.    INVESTMENT RISK

      Investment securities, in general, are exposed to various risks, such as
      interest rate, credit and overall market volatility risks. Further, due to
      the level of risk associated with certain investment securities, it is
      reasonably possible that changes in the values of investment securities
      will occur in the near term and that such changes could materially affect
      the amounts reported in the accompanying statements of net assets
      available for benefits.

9.    PLAN CHANGES

      Effective January 1, 2005, the Plan was amended as follows:

        Clarified that an Eligible Employee did not include nonresident aliens
        with no United States source income,

        Provided that individuals who were terminated in connection with the
        transition of certain information technology-related responsibilities
        from the Company will be entitled to receive a profit-sharing
        contribution for 2004 even if they are not employed by the Company and
        its affiliates on December 31, 2004,

        Clarified the Plan's disability provisions,

        Reduced the amount to which an involuntary cash-out applies from
        $5,000 to $1,000 and provided that such determination shall be
        made after taking into account rollover contributions, and

        Clarified the Plan's ERISA Section 404(c) provisions.

      Effective October 1, 2005, the Plan was amended to allow employees to
      transfer funds out of the Cinergy Corp. Common Stock Master Trust to other
      investment options at any time.

      Effective January 1, 2006, the Plan was amended as follows:

        Clarified that it will no longer be a 401(k) safe harbor plan for plan
        years beginning after December 31, 2005

        Permitted eligible employees to make pre-tax and after-tax
        contributions from overtime pay, but without Cinergy matching
        those contributions

10.   SUBSEQUENT EVENT

      On April 3, 2006, the merger of Cinergy Corp. and Duke Energy was
      finalized. Shares of Cinergy common stock within the Plan were exchanged
      for shares of Duke Energy common stock. Effective April 3, 2006, the
      Cinergy Stock Fund was renamed the Duke Stock Fund.



                                    ******




                              SUPPLEMENTAL SCHEDULE




CINERGY CORP.
UNION EMPLOYEES' 401(k) PLAN

EIN: 31-1385023
PLAN NUMBER: 101

SCHEDULE H, PART IV, LINE 4i--SCHEDULE OF ASSETS (HELD AT END OF YEAR)
DECEMBER 31, 2005
- --------------------------------------------------------------------------


  Identity of Issuer,     Description of Investment, Including
  Borrower, Lessor,       Maturity Date, Rate of Interest,             Current
    or Similar Party      Collateral, and Par or Maturity Value         Value

*Fidelity Investments     Magellan Fund                             $25,656,918
*Fidelity Investments     Equity Income Fund                         17,792,544
*Fidelity Investments     U.S. Bond Index Fund                        4,709,361
*Fidelity Investments     Diversified International Stock Fund        6,129,719
*Fidelity Investments     Low-Priced Stock Fund                       8,623,056
*Fidelity Investments     Freedom Income Fund                           320,057
*Fidelity Investments     Freedom 2000 Fund                             458,570
*Fidelity Investments     Freedom 2010 Fund                           3,629,193
*Fidelity Investments     Freedom 2020 Fund                           1,862,134
*Fidelity Investments     Freedom 2030 Fund                           1,009,858
*Fidelity Investments     Freedom 2040 Fund                             474,095
*Fidelity Investments     Blue Chip Fund                              2,857,188
 TCW Asset Management     TCW Galileo Value Opportunity Fund            356,492
 Rainier Investments      Rainier Small/Midcap I                      5,713,273
                                                                  -------------

                           Total investments in mutual funds         79,592,458
                                                                   ------------

*Cinergy Corp. Common     Plan interest in Master Trust              59,234,427
   Stock Master Trust
 JP Morgan Investments    JP Morgan Prime Money Market Instrument     9,985,945
*Fidelity Investments     Fidelity Managed Income Portfolio             861,349
*Fidelity Investments     US Equity Index Pool                        1,329,750
*Various Plan             Participant Loans (interest rates ranging
   Participants           from 6.25% to 7.75% and maturities
                          through July 2, 2010)                       4,602,558

*Denotes a party-in-interest.




                                 SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Plan
Committee has duly caused this annual report to be signed on its behalf by the
undersigned hereunto duly authorized.


                         CINERGY CORP. UNION EMPLOYEES'
                                   401(K) PLAN


                           By /s/ Darlene Glesenkamp

                               Plan Administrator




                                                                   EXHIBIT 23


CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM


We consent to the incorporation by reference in Registration Statement No.
333-72900 on Form S-8 of our report dated June 23, 2006, relating to the
financial statements of the Cinergy Corp. Union Employees' 401(k) Plan appearing
in this Annual Report on Form 11-K of the Cinergy Corp. Union Employees' 401(k)
Plan for the year ended December 31, 2005.



Cincinnati, Ohio
June 27, 2006