As filed with the Securities and
    Exchange Commission on July 1, 2011
 Registration
    No. 333-
      UNITED STATES SECURITIES AND
    EXCHANGE COMMISSIONWashington, D.C.
    20549
      Form S-3
  REGISTRATION STATEMENT
    UNDER
    THE SECURITIES ACT OF 1933
      FIRST POTOMAC REALTY
    TRUST
 (Exact Name of Registrant as
    Specified in Its Charter)
  Maryland(State or Other Jurisdiction
    of
    Incorporation or Organization)

37-1470730(I.R.S. Employer
    Identification Number)       7600 Wisconsin Avenue, 11th
    Floor
    Bethesda, MD 20814(301) 986-9200 (Address, Including
    Zip Code, and Telephone Number, Including Area Code, of
    Registrants Principal Executive Offices)
      Joel F. Bonder
    Executive Vice President, General Counsel
    and Secretary
    First Potomac Realty Trust
    7600 Wisconsin Avenue, 11th Floor
    Bethesda, MD 20814(301) 986-9200 (Name, Address,
    Including Zip Code, and Telephone Number, Including Area Code,
    of Agent For Service)
      Copy to:David P. Slotkin
    Hogan Lovells US LLP
    555 Thirteenth Street, NW
    Washington, D.C.
    20004-1109(202) 637-5600
  Approximate date of commencement of proposed sale to the
    public:
  o
  þ
  o
  o
  þ
  o
  Rule 12b-2
  Large accelerated
    filer o

Accelerated
    filer þ

Non-accelerated
    filer o
    (Do not check if a smaller reporting company)

Smaller reporting
    company o   CALCULATION
    OF REGISTRATION FEE
  Proposed Maximum


Proposed Maximum


Amount ofTitle of Each Class of


Amount


Offering


Aggregate


RegistrationSecurities to be Registered(1)


to be Registered


Price Per Share


Offering Price


Fee(1)(2)Common Shares of beneficial interest, par value $0.001 per
    share(3)Preferred Shares of beneficial interest, par value $0.001 per
    share(3)Depositary Shares, representing Preferred Shares(3)Warrants(3)(4)Rights(3)Total   (1)
    
    The securities covered by this
    registration statement may be sold or otherwise distributed
    separately, together or as units with other securities covered
    by this registration statement. This registration statement
    covers offers, sales and other distributions of the securities
    listed in this table from time to time at prices to be
    determined. This registration statement also covers common
    shares, preferred shares, depositary shares, warrants, rights
    and that may be offered or sold under delayed delivery contracts
    pursuant to which the counterparty may be required to purchase
    such securities, as well as such contracts themselves. Such
    contracts would be issued with the securities.(2)
    
    In accordance with
    Rules 456(b) and 457(r) under the Securities Act of 1933,
    as amended, the Company is deferring payment of all of the
    registration fee.(3)
    
    This registration statement covers
    an indeterminate amount of the securities of each identified
    class of securities. An unspecified aggregate initial offering
    price or number of the securities of each identified class is
    being registered as may from time to time be offered at
    unspecified prices. Separate consideration may or may not be
    received for securities that are issuable on exercise,
    conversion or exchange of other securities or that are
    represented by depositary shares.(4)
    
    The warrants covered by this
    registration statement may be warrants for common shares,
    preferred shares or depositary shares.




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PROSPECTUS
  
  Common Shares
 Preferred Shares
 Depositary Shares
 Warrants
 Rights
    
    Common shares of beneficial interest, par value $0.001 per
    share, or common shares;
    Preferred shares of beneficial interest, par value $0.001 per
    share, or preferred shares;
    Depositary shares representing our preferred shares;
    Warrants to purchase our common shares, preferred shares or
    depositary shares representing preferred shares; and
    Rights to purchase our common shares.      (301) 986-9200.
  Investing in our securities involves risks. See Risk
    Factors beginning on page 2 of this prospectus for
    certain risk factors to consider before you decide to invest in
    the securities offered hereby.
  Neither the Securities and Exchange Commission nor any state
    securities commission has approved or disapproved of these
    securities or passed upon the adequacy or accuracy of this
    prospectus. Any representation to the contrary is a criminal
    offense.




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TABLE OF
    CONTENTS
  About this Prospectus


iiForward-Looking Statements


iiOur Company


1Risk Factors


2Use of Proceeds


2Ratio of Earnings to Combined Fixed Charges and
    Preferred Dividends


2Description of Common Shares


3Description of Preferred Shares


10Description of Depositary Shares


12Description of Warrants


16Description of Rights


17Restrictions on Ownership and Transfer


18Material U.S. Federal Income Tax Consequences


21Book-Entry Securities


50Plan of Distribution


52Legal Matters


54Experts


54Where to Find Additional Information


54Incorporation of Certain Information by
    Reference


55   i




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ABOUT
    THIS PROSPECTUS         FORWARD-LOOKING
    STATEMENTS   ii




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Form 10-K Form 10-K
 iii




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OUR
    COMPANY        th (301) 986-9200. http://www.first-potomac.com
 1




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RISK
    FACTORS  Form 10-K
 USE OF
    PROCEEDS  and/or
 RATIO OF
    EARNINGS TO COMBINED FIXED CHARGES AND PREFERRED
    DIVIDENDS    Three MonthsEnded

Years Ended December 31,March 31, 2011

2010

2009

2008

2007

2006Ratio of earnings to combined fixed charges and preferred
    dividends


*



*



1.16



1.06



*



*     *
    
    Fixed charges and preferred dividends exceeded earnings for the
    three months ended March 31, 2011 and for each of the years
    ended December 31, 2010, 2007 and 2006. The amounts of the
    deficiencies, or the fixed charge and preferred dividend amounts
    in excess of earnings, were $5.9 million for the three
    months ended March 31, 2011 and $9.4 million,
    $5.3 million and $0.8 million for the years ended
    December 31, 2010, 2007 and 2006, respectively. 2




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DESCRIPTION
    OF COMMON SHARES  General
      Voting
    Rights of Common Shares
      Dividends,
    Liquidation and Other Rights
      Power to
    Classify and Reclassify Shares, Increase Authorized Shares and
    Issue Additional Shares
   3




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Transfer
    Agent and Registrar
    Certain
    Provisions of Maryland Law and Our Declaration of Trust and
    Bylaws
  The following summary of certain provisions of Maryland law
    and of our declaration of trust and bylaws does not purport to
    be complete and is subject to and qualified in its entirety by
    reference to Maryland law and to our declaration of trust and
    bylaws. See Where To Find Additional Information for
    information on how to obtain documents from us, including our
    declaration of trust and bylaws.
  Our
    Board of Trustees
        Removal
    of Trustees
   4




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Business
    Combinations
    
    any person who beneficially owns, directly or indirectly, 10% or
    more of the voting power of the trusts outstanding voting
    shares; or
    an affiliate or associate of the trust who, at any time within
    the two-year period prior to the date in question, was the
    beneficial owner, directly or indirectly, of 10% or more of the
    voting power of the then-outstanding voting shares of the trust.      
    80% of the votes entitled to be cast by holders of outstanding
    voting shares of the trust; and
    two-thirds of the votes entitled to be cast by holders of voting
    shares of the trust other than shares held by the interested
    shareholder with whom (or with whose affiliate) the business
    combination is to be effected or shares held by an affiliate or
    associate of the interested shareholder.    Control
    Share Acquisitions
   5




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
    one-tenth or more but less than one-third;
    one-third or more but less than a majority; or
    a majority or more of all voting power.          Subtitle
    8
    
    a classified board;
    a two-thirds shareholder vote requirement for removing a trustee;
    a requirement that the number of trustees be fixed only by vote
    of the trustees;
    a requirement that a vacancy on the board be filled only by the
    remaining trustees and for the remainder of the full term of the
    class of trustees in which the vacancy occurred; and
    a requirement that requires the request of the holders of at
    least a majority of all votes entitled to be cast to call a
    special meeting of shareholders.   6




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Amendment
    of Our Declaration of Trust and Bylaws and Approval of
    Extraordinary Transactions
      Meetings
    of Shareholders
    Advance
    Notice of Trustee Nominations and New Business
    
    pursuant to our notice of the meeting;
    by or at the direction of our board of trustees; or
    by a shareholder who was a shareholder of record at the time of
    the provision of notice who is entitled to vote at the meeting
    and has complied with the advance notice procedures set forth in
    our bylaws.    
    pursuant to our notice of the meeting;
    by or at the direction of our board of trustees; or 7




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
    provided that our board of trustees has determined that trustees
    shall be elected at such meeting, by a shareholder who was a
    shareholder of record at the time of the provision of notice who
    is entitled to vote at the meeting and has complied with the
    advance notice provisions set forth in our bylaws.    Anti-takeover
    Effect of Certain Provisions of Maryland Law and of Our
    Declaration of Trust and Bylaws
    Share
    Ownership Limit
    REIT
    Qualification
    Indemnification
    and Limitation of Trustees and Officers
    Liability
     8




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
    the act or omission of the director or officer was material to
    the matter giving rise to the proceeding and (1) was
    committed in bad faith or (2) was the result of active and
    deliberate dishonesty;
    the director or officer actually received an improper personal
    benefit in money, property or services; or
    in the case of any criminal proceeding, the director or officer
    had reasonable cause to believe that the act or omission was
    unlawful.      
    a written affirmation by such director or officer of his or her
    good faith belief that he or she has met the standard of conduct
    necessary for indemnification by the corporation; and
    a written undertaking by such director or officer or on such
    directors or officers behalf to repay the amount
    paid or reimbursed by the corporation if it is ultimately
    determined that the director did not meet the standard of
    conduct.    
    any present or former trustee, officer or shareholder (including
    any individual who while a trustee or officer and at our
    request, serves or has served another corporation, partnership,
    joint venture, trust, employee benefit plan or any other
    enterprise as a director, officer, partner or trustee), who has
    been successful, on the merits or otherwise, against reasonable
    expenses incurred by such person in the defense of a proceeding
    to which the trustee, officer or shareholder was made a party by
    reason of such status;
    any present or former trustee or officer against any claim or
    liability to which such trustee or officer may become subject by
    reason of such status; and
    any present or former shareholder against any claim or liability
    to which such person may become subject by reason of such
    persons status as a present or former shareholder.     9




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DESCRIPTION
    OF PREFERRED SHARES  General
    Outstanding
    Preferred Shares
      Future
    Series of Preferred Shares
        
    the title and stated value of such preferred shares;
    the number of such preferred shares offered, the liquidation
    preference per share and the offering price of such preferred
    shares;
    the dividend rate(s), period(s)
    and/or
    payment date(s) or method(s) of calculation thereof applicable
    to such preferred shares; 10




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
    whether dividends shall be cumulative or non-cumulative and, if
    cumulative, the date from which dividends on such preferred
    shares shall accumulate;
    the procedures for any auction and remarketing, if any, for such
    preferred shares;
    the provisions for a sinking fund, if any, for such preferred
    shares;
    the provisions for repurchase or redemption, if applicable, of
    such preferred shares;
    any listing of such preferred shares on any securities exchange;
    the terms and conditions, if applicable, upon which such
    preferred shares will be convertible into our common shares,
    including the conversion price (or manner of calculation
    thereof) and conversion period;
    a discussion of material federal income tax consequences
    applicable to such preferred shares;
    any limitations on issuance of any series of preferred shares
    ranking senior to or on a parity with such series of preferred
    shares as to dividend rights and rights upon liquidation,
    dissolution or winding up of our affairs;
    in addition to those limitations described herein, any other
    limitations on actual and constructive ownership and
    restrictions on transfer, in each case as may be appropriate to
    preserve our status as a REIT;
    the voting rights of the preferred shares, if any; and
    any other specific terms, preferences, rights, limitations or
    restrictions of such preferred shares.  Certain
    Provisions of Maryland Law and Our Declaration of Trust and
    Bylaws
   11




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DESCRIPTION
    OF DEPOSITARY SHARES  General
      Dividends
    and Other Distributions
        Withdrawal
    of Shares
   12




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Redemption
    of Depositary Shares
      Voting of
    the Preferred Shares
    Liquidation
    Preference
    Conversion
    of Preferred Shares
   13




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Amendment
    and Termination of Deposit Agreement
      Charges
    of Preferred Shares Depositary
    Resignation
    and Removal of Depositary
   14




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Miscellaneous
        Restrictions
    on Ownership
   15




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DESCRIPTION
    OF WARRANTS      
    the title and issuer of such warrants;
    the aggregate number of such warrants;
    the price or prices at which such warrants will be issued;
    the currencies in which the price or prices of such warrants may
    be payable;
    the designation, amount and terms of the securities purchasable
    upon exercise of such warrants;
    the designation and terms of the other securities with which
    such warrants are issued and the number of such warrants issued
    with each such security;
    if applicable, the date on and after which such warrants and the
    securities purchasable upon exercise of such warrants will be
    separately transferable;
    the price or prices at which and currency or currencies in which
    the securities purchasable upon exercise of such warrants may be
    purchased;
    the date on which the right to exercise such warrants shall
    commence and the date on which such right shall expire;
    the minimum or maximum amount of such warrants which may be
    exercised at any one time;
    information with respect to book-entry procedures, if any;
    a discussion of material federal income tax
    consequences; and
    any other material terms of such warrants, including terms,
    procedures and limitations relating to the exchange and exercise
    of such warrants. 16




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DESCRIPTION
    OF RIGHTS      
    the date for determining the shareholders entitled to the rights
    distribution;
    the aggregate number of common shares purchasable upon exercise
    of such rights and the exercise price;
    the aggregate number of rights being issued;
    the date, if any, on and after which such rights may be
    transferable separately;
    the date on which the right to exercise such rights shall
    commence and the date on which such right shall expire;
    a discussion of material federal income tax
    consequences; and
    any other terms of such rights, including terms, procedures and
    limitations relating to the distribution, exchange and exercise
    of such rights. 17




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RESTRICTIONS
    ON OWNERSHIP AND TRANSFER         18




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19




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20




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MATERIAL
    U.S. FEDERAL INCOME TAX CONSEQUENCES    
    A tax-exempt organization, except to the extent discussed below
    in  Taxation of Shareholders 
    Taxation of Tax-Exempt U.S. Shareholders;
    A broker-dealer;
    A
    non-U.S. shareholder
    (as defined below), except to the extent discussed below in
     Taxation of Shareholders  Taxation
    of
    Non-U.S. Shareholders;
    A trust, estate, regulated investment company, REIT, financial
    institution, insurance company or S corporation;
    A person subject to the alternative minimum tax provisions of
    the Internal Revenue Code;
    A person holding our securities as part of a hedge,
    straddle, conversion transaction,
    synthetic security or other integrated investment;
    A person holding our securities through a partnership or similar
    pass-through entity;
    A person holding 10% or more (by value or vote) of our
    outstanding securities;
    A person who receives our securities through the exercise of
    employee share options or otherwise as compensation; or
    A U.S. expatriate.    
    This summary does not address state, local or
    non-U.S. tax
    considerations;
    This summary deals only with investors that hold our securities
    as a capital asset within the meaning of
    Section 1221 of the Internal Revenue Code; and
    This discussion is not intended to be, and should not be
    construed as, tax advice.   21




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We urge you to consult your own tax advisor regarding the
    specific tax consequences to you of ownership of our securities
    and of our election to be taxed as a REIT. Specifically, you
    should consult your own tax advisor regarding the federal,
    state, local, foreign, and other tax consequences of such
    ownership and election, and regarding potential changes in
    applicable tax laws.
  Taxation
    of our Company
        
    We are subject to the corporate federal income tax on any
    REIT taxable income, including net capital gain,
    that we do not distribute to shareholders during, or within a
    specified time period after, the calendar year in which the
    income is earned. REIT taxable income is the
    otherwise taxable income of the REIT subject to certain
    adjustments, including a deduction for dividends paid.
    We may be subject to the corporate alternative minimum
    tax on any items of tax preference, including any
    deductions of net operating losses.
    We are subject to tax, at the highest corporate rate, on: net
    income from the sale or other disposition of foreclosure
    property that we hold primarily for sale to customers in
    the ordinary course of business, and other non-qualifying income
    from foreclosure property. In general, foreclosure
    property is property acquired by us as a result of having
    bid in a foreclosure or through other legal means subsequent to
    a default on a lease of such property or on an indebtedness
    secured by such property.
    We are subject to a 100% tax on net income from prohibited
    transactions. In general, prohibited
    transactions are sales or other dispositions of property,
    other than foreclosure property, that we hold primarily for sale
    to customers in the ordinary course of business.
    If we fail to satisfy one or both of the 75% gross income test
    or the 95% gross income test, as described below under
     Requirements for Qualification 
    Gross Income Tests, but our failure is due to reasonable
    cause and not due to willful neglect and we nonetheless continue
    to qualify as a REIT because we meet other requirements, we will
    be subject to a 100% tax on the greater of (1) the amount
    by which 95% (or 90% for our 2003 and 2004 taxable years only)
    of our gross income exceeds the amount of our gross income
    qualifying under the 95% gross income test, (2) the amount
    by which we fail the 75% gross income test, or multiplied, in
    either case, by a fraction intended to reflect our profitability.
    If we fail to distribute during a calendar year at least the sum
    of: (1) 85% of our REIT ordinary income for the year,
    (2) 95% of our REIT capital gain net income for the year,
    and (3) any undistributed taxable income required to be
    distributed from earlier periods, then we will be subject to a
    4% nondeductible excise tax on the excess of the required
    distribution over the amount we actually distributed and amounts
    retained but with respect to which federal income tax was paid. 22




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
    If we fail any of the asset tests (other than a de minimis
    failure of the 5% asset test or the 10% vote or value test), as
    described below under  Requirements for
    Qualifications  Asset Tests, as long as
    (1) the failure was due to reasonable cause and not to
    willful neglect, (2) we timely file a description of each
    asset that caused such failure with the IRS, and (3) we
    dispose of the assets or otherwise comply with the asset tests
    within six months after the last day of the quarter in which we
    identify such failure, we will pay a tax equal to the greater of
    $50,000 or the amount determined by multiplying the net income
    generated by the nonqualifying assets during the period in which
    we failed to satisfy the asset tests by the highest tax rate
    applicable to corporations during this time period.
    If we fail to satisfy one or more requirements for REIT
    qualification, other than the gross income tests and the asset
    tests, and such failure is due to reasonable cause and not to
    willful neglect, and we nonetheless maintain our qualification
    as a REIT because the requirements of certain relief provisions
    are satisfied, we will be required to pay a penalty of $50,000
    for each such failure.
    We may elect to retain and pay income tax on our net long-term
    capital gain. In that case, a U.S. shareholder would be
    taxed on its proportionate share of our undistributed long-term
    capital gain (to the extent that we make a timely designation of
    such gain to the shareholder), receive a credit or refund for
    its proportionate share of the tax we paid, and increase its
    basis in our shares.
    We will be subject to a 100% excise tax on transactions with a
    taxable REIT subsidiary that are not conducted on an
    arms-length basis.
    If we acquire any asset from a C corporation, or a corporation
    that generally is subject to full corporate-level tax, carryover
    basis transaction, we will be liable for corporate income tax,
    at the highest applicable corporate rate, on the built-in
    gain with respect to those assets at the time we acquired
    them if we dispose of those assets within 10 years after
    acquiring them (provided no election is made for the transaction
    be currently taxable). Built-in gain is the amount
    by which an assets fair market value exceeds its adjusted
    tax basis at the time we acquired the asset.
    We may be required to pay monetary penalties to the IRS in
    certain circumstances, including if we fail to meet
    record-keeping requirements intended to monitor our compliance
    with rules relating to the composition of a REITs
    shareholders, as described below in
     Requirements for Qualification 
    Recordkeeping Requirements.
    The earnings of our lower-tier entities that are subchapter C
    corporations, including taxable REIT subsidiaries, are subject
    to federal corporate income tax.  and/or
  Requirements
    for Qualification
    Organizational
    Requirements
         23




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Effect
    of Subsidiary Entities
  Ownership
    of Qualified REIT Subsidiaries
   24




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Ownership
    of Taxable REIT Subsidiaries
           25




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Ownership
    of Partnership Interests
    Gross
    Income Tests
    
    rents from real property;
    interest on debt secured by mortgages on real property or on
    interests in real property;
    dividends or other distributions on, and gain from the sale of,
    shares in other REITs;
    gain on the disposition of real property or mortgages on real
    property, in either case, not held for sale to
    customers; and
    income derived from the temporary investment of new capital in
    stock or debt instruments during the one-year period following
    our receipt of the new capital that we raise through the
    issuance of our shares of beneficial interest or a public
    offering of our debt with a maturity date of at least five years.      Rents
    from Real Property
   26




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
    are fixed at the time the leases are entered into;
    are not renegotiated during the term of the leases in a manner
    that has the effect of basing percentage rent on income or
    profits; and
    conform with normal business practice.         27




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Interest
    Income
    Prohibited
    Transactions Tax
   28




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
    the REIT has held the property for not less than four years (or,
    for sales made after July 30, 2008, two years) and for the
    production of rental income (unless such property was acquired
    through foreclosure or a deed in lieu of foreclosure or a lease
    termination);  
    the capitalized expenditures made by the REIT, or any partner of
    the REIT, during the four-year period (or, for sales made after
    July 30, 2008, two-year period) preceding the date of the
    sale that are includable in the basis of the property are less
    than 30% of the net selling prince of the property;  
    either (1) during the year in question, the REIT did not
    make more than seven sales of property other than foreclosure
    property or sales to which Section 1033 of the Internal
    Revenue Code applies, (2) the aggregate adjusted bases of
    all such properties sold by the REIT during the year did not
    exceed 10% of the aggregate bases of all of the assets of the
    REIT at the beginning of the year or (3) for sales made
    after July 30, 2008, the aggregate fair market value of all
    such properties sold by the REIT during the year did not exceed
    10% of the aggregate fair market value of all of the assets of
    the REIT at the beginning of the year;  
    in the case of property not acquired through foreclosure or
    lease termination, the REIT has held the property for at least
    four years (or, for sales made after July 30, 2008, two
    years) for the production of rental income; and  
    if the REIT has made more than seven sales of non-foreclosure
    property during the taxable year, substantially all of the
    marketing and development expenditures with respect to the
    property were made through an independent contractor from whom
    the REIT derives no income.    Income
    from Foreclosure Property
    
    that is acquired by a REIT as the result of the REIT having bid
    on such property at foreclosure, or having otherwise reduced
    such property to ownership or possession by agreement or process
    of law, after there was a default or default was imminent on a
    lease of such property or on indebtedness that such property
    secured;
    for which the related loan or leased property was acquired by
    the REIT at a time when the default was not imminent or
    anticipated; and
    for which the REIT makes a proper election to treat the property
    as foreclosure property.  mortgagee-in-possession
 29




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
    on which a lease is entered into for the property that, by its
    terms, will give rise to income that does not qualify for
    purposes of the 75% gross income test (other than income and
    gain derived from foreclosure property), or any amount is
    received or accrued, directly or indirectly, pursuant to a lease
    entered into on or after such day that will give rise to income
    that does not qualify for purposes of the 75% gross income test;
    on which any construction takes place on the property (other
    than completion of a building, or any other improvement, where
    more than 10% of the construction was completed before default
    became imminent); or
    which is more than 90 days after the day on which the REIT
    acquired the property and the property is used in a trade or
    business which is conducted by the REIT (other than through an
    independent contractor from whom the REIT itself does not derive
    or receive any income).  Income
    from Hedging Transactions
    Foreign
    Currency Gains
   30




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Temporary
    Investment Income
    Failure
    to Satisfy Gross Income Tests
    
    our failure to meet these tests was due to reasonable cause and
    not to willful neglect;
    we attached a schedule of the sources of our income to our tax
    return; and
    any incorrect information on the schedule is not due to fraud
    with intent to evade tax.    
    our failure to meet those tests is due to reasonable cause and
    not to willful neglect; and
    following such failure for any taxable year, a schedule of the
    sources of our income is filed with the IRS in accordance with
    regulations prescribed by the Secretary of the Treasury.    Asset
    Tests
           31




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
    Straight debt securities, which is defined as a
    written unconditional promise to pay on demand or on a specified
    date a sum certain in money if (i) the debt is not
    convertible, directly or indirectly, into stock, and
    (ii) the interest rate and interest payment dates are not
    contingent on profits, the borrowers discretion, or
    similar factors. Straight debt securities do not
    include any securities issued by a partnership or a corporation
    in which we or any controlled taxable REIT subsidiary hold
    non-straight debt securities that have an aggregate
    value of more than 1% of the issuers outstanding
    securities. However, straight debt securities
    include debt subject to the following contingencies: (A) a
    contingency relating to the time of payment of interest or
    principal, as long as either (i) there is no change to the
    effective yield of the debt obligation, other than a change to
    the annual yield that does not exceed the greater of 0.25% or 5%
    of the annual yield, or (ii) neither the aggregate issue
    price nor the aggregate face amount of the issuers debt
    obligations held by us exceeds $1 million and no more than
    12 months of unaccrued interest on the debt obligations can
    be required to be prepaid; and (B) a contingency relating
    to the time or amount of payment upon a default or prepayment of
    a debt obligation, as long as the contingency is consistent with
    customary commercial practice.
    Any loan to an individual or an estate.
    Any section 467 rental agreement, other
    than an agreement with a related party tenant.
    Any obligation to pay rents from real property.
    Certain securities issued by governmental entities.
    Any security issued by a REIT.
    Any debt instrument issued by an entity treated as a partnership
    for federal income tax purposes in which we are a partner to the
    extent of our proportionate interest in the debt and equity
    securities of the partnership.
    Any debt instrument issued by an entity treated as a partnership
    for federal income tax purposes not described in the preceding
    bullet points if at least 75% of the partnerships gross
    income, excluding income from prohibited transactions, is
    qualifying income for purposes of the 75% gross income test
    described above in  Requirements for
    Qualification  Gross Income Tests.      
    we satisfied the asset tests at the end of the preceding
    calendar quarter; and
    the discrepancy between the value of our assets and the asset
    test requirements arose from changes in the market values of our
    assets. 32




---



##### 



30-days 30-day
  Distribution
    Requirements
    
    the sum of (a) 90% of our REIT taxable income,
    computed without regard to the dividends paid deduction and our
    net capital gain or loss, and (b) 90% of our after-tax net
    income, if any, from foreclosure property, minus
    the sum of certain items of non-cash income.        built-in-gain Built-in-gain
   33




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##### 




    85% of our REIT ordinary income for the year,
    95% of our REIT capital gain income for the year, and
    any undistributed taxable income from prior periods net of
    excess distributions from prior taxable periods,      Recordkeeping
    Requirements
    Failure
    to Qualify as a Reit
     34




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##### 



Other Tax
    Consequences
  Tax
    Aspects of Our Investments in Partnerships and Limited Liability
    Companies Generally
    Classification
    as Partnerships
    
    is treated as a partnership under the Treasury regulations
    relating to entity classification (the
    check-the-box
    regulations); and
    is not a publicly traded partnership.  check-the-box
       35




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##### 



Income
    Taxation of the Partnerships and Their Partners
  Partners,
    Not the Partnerships, Subject to Tax
    Tax
    Allocations With Respect to Contributed Properties
    Basis in
    Partnership Interest
    
    the amount of cash and the basis of any other property we
    contribute to the partnership;
    increased by our allocable share of the partnerships
    income (including tax-exempt income) and our allocable share of
    indebtedness of the partnership; and
    reduced, but not below zero, by our allocable share of the
    partnerships loss, the amount of cash and the basis of
    property distributed to us, and constructive distributions
    resulting from a reduction in our share of indebtedness of the
    partnership.   36




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##### 



Depreciation
    Deductions Available to Partnerships
    
    Qualified leasehold improvement property generally
    includes improvements made to the interior of nonresidential
    real property that are placed in service more than three years
    after the date the building was placed in service.
    A first-year bonus depreciation deduction equal to
    50% of the adjusted basis of qualified property is available for
    qualified property that is acquired after
    December 31, 2007 and before January 1, 2009, and that
    is placed in service before January 1, 2009.
    Qualified property includes qualified leasehold
    improvement property (as defined above) and property with a
    recovery period of less than 20 years such as furnishings
    and equipment.    Sale of a
    Partnerships Property
   37




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##### 



Taxation
    of Shareholders
  Taxation
    of Taxable U.S. Shareholders
    
    a citizen or resident of the United States;  
    a corporation (including an entity treated as a corporation for
    U.S. federal income tax purposes) created or organized in
    or under the laws of the United States or of a political
    subdivision thereof (including the District of Columbia);  
    an estate the income of which is subject to U.S. federal
    income taxation regardless of its source; or  
    any trust if (1) a U.S. court is able to exercise
    primary supervision over the administration of such trust and
    one or more U.S. persons have the authority to control all
    substantial decisions of the trust, or (2) it has a valid
    election in place to be treated as a U.S. person.    Distributions
    Generally
    Distributions
    to Holders of Depositary Shares
   38




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##### 



Capital
    Gain Dividends
  89-81, Form 1099-DIV
      
    a long-term capital gain distribution, which would be taxable to
    non-corporate U.S. shareholders at a maximum rate of 15%
    (through 2012, but scheduled to increase to 20% on or after
    January 1, 2013), and taxable to U.S. shareholders
    that are corporations at a maximum rate of 35%;  
    an unrecaptured Section 1250 gain distribution,
    which would be taxable to non-corporate U.S. shareholders
    at a maximum rate of 25%, to the extent of previously claimed
    depreciation deductions.  provided
    Qualified
    Dividend Income
  121-day
 39




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##### 




    the qualified dividend income received by us during such taxable
    year from non-REIT corporations (including our taxable REIT
    subsidiaries);  
    the excess of any undistributed REIT taxable income
    recognized during the immediately preceding year over the
    U.S. federal income tax paid by us with respect to such
    undistributed REIT taxable income; and  
    the excess of (i) any income recognized during the
    immediately preceding year attributable to the sale of a
    built-in-gain
    asset that was acquired in a carry-over basis transaction from a
    C corporation with respect to which the Company is
    required to pay U.S. federal income tax, over (ii) the
    U.S. federal income tax paid by us with respect to such
    built-in gain.  Form 1099-DIV
  Passive
    Activity Losses and Investment Interest Limitations
    Dispositions
    of Our Shares
     40




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##### 



Redemption
    of Preferred and Depositary Shares
    Non-U.S. Shareholders 
 41




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##### 



share-by-share
  Conversion
    of Our Preferred Shares into Common Shares
    Medicare
    Tax on Unearned Income
    Taxation
    of Tax-Exempt U.S. Shareholders
     42




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##### 




    either (1) one pension trust owns more than 25% of the
    value of our stock, or (2) one or more pension trusts, each
    individually holding more than 10% of the value of our shares,
    collectively own more than 50% of the value of our
    shares; and  
    we would not have qualified as a REIT but for the fact that
    Section 856(h)(3) of the Code provides that shares owned by
    such trusts shall be treated, for purposes of the requirement
    that not more than 50% of the value of the outstanding shares of
    a REIT is owned, directly or indirectly, by five or fewer
    individuals (as defined in the Code to include
    certain entities), as owned by the beneficiaries of such trusts.    Taxation
    of Non-U.S.
    Shareholders
  non-U.S. shareholders. non-U.S. shareholder non-U.S. shareholder
  Distributions
    Generally
    
    ordinary income dividends;  
    long-term capital gain; or  
    return of capital distributions.   43




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##### 



Ordinary
    Income Dividends
  non-U.S. shareholder
  
    not attributable to our net capital gain; or  
    the distribution is attributable to our net capital gain from
    the sale of U.S. Real Property Interests, or
    USRPIs, and the
    non-U.S. shareholder
    owns 5% or less of the value of our securities at all times
    during the one-year period ending on the date of the
    distribution.  non-U.S. shareholders non-U.S. shareholders non-U.S. shareholders non-U.S. shareholder non-U.S. shareholder. non-U.S. shareholder
  non-U.S. shareholder
  
    a lower treaty rate applies and the
    non-U.S. shareholder
    files an IRS
    Form W-8BEN
    evidencing eligibility for that reduced treaty rate with
    us; or  
    the
    non-U.S. shareholder
    files an IRS
    Form W-8ECI
    with us claiming that the distribution is income effectively
    connected with the
    non-U.S. shareholders
    trade or business.  Return of
    Capital Distributions
  non-U.S. shareholders non-U.S. shareholder non-U.S. shareholder non-U.S. shareholder non-U.S. shareholder non-U.S. shareholder non-U.S. shareholders non-U.S. shareholders
 44




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##### 



Capital
    Gain Dividends
  non-U.S. shareholder
  
    the distribution is attributable to our net capital gain (other
    than from the sale of USRPIs) and we timely designate the
    distribution as a capital gain dividend; or  
    the distribution is attributable to our net capital gain from
    the sale of USRPIs and the
    non-U.S. common
    shareholder owns more than 5% of the value of our securities at
    any point during the one-year period ending on the date on which
    the distribution is paid.  non-U.S. shareholder non-U.S. shareholder
  
    the
    non-U.S. shareholders
    investment in our securities is effectively connected with a
    U.S. trade or business of the
    non-U.S. shareholder,
    in which case the
    non-U.S. shareholder
    will be subject to the same treatment as U.S. shareholders
    with respect to any gain, except that a
    non-U.S. shareholder
    that is a corporation also may be subject to the 30% branch
    profits tax; or  
    the
    non-U.S. shareholder
    is a nonresident alien individual who is present in the United
    States for 183 days or more during the taxable year and has
    a tax home in the United States in which case the
    nonresident alien individual will be subject to a 30% tax on his
    capital gains.  non-U.S. shareholder non-U.S. shareholder
  non-U.S. shareholder non-U.S. shareholder, non-U.S. shareholders non-U.S. shareholder
  Undistributed
    Capital Gain
  non-U.S. shareholders non-U.S. shareholder non-U.S. shareholder, non-U.S. shareholders non-U.S. shareholder
 45




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##### 



Dispositions
    of Our Securities
  non-U.S. shareholder
  
    Fifty percent or more of our assets on any of certain testing
    dates during a prescribed testing period consist of interests in
    real property located within the United States, excluding for
    this purpose, interests in real property solely in a capacity as
    creditor;  
    We are not a domestically-controlled qualified investment
    entity. A domestically-controlled qualified investment
    entity includes a REIT, less than 50% of value of which is held
    directly or indirectly by
    non-U.S. shareholders
    at all times during a specified testing period. Although we
    believe that we are and will remain a domestically-controlled
    REIT, because our shares are publicly traded, we cannot
    guarantee that we are or will remain a domestically-controlled
    qualified investment entity; and  
    Either (a) our securities are not regularly
    traded, as defined by applicable Treasury regulations, on
    an established securities market; or (b) our securities are
    regularly traded on an established securities market
    and the selling
    non-U.S. shareholder
    has held over 5% of our outstanding securities any time during
    the five-year period ending on the date of the sale.  non-U.S. shareholder 30-day non-U.S. shareholder 61-day
  non-U.S. shareholder
  non-U.S. shareholder non-U.S. shareholders non-U.S. shareholder, non-U.S. shareholder non-U.S. shareholder
  Conversion
    of Our Preferred Shares into Common Shares
  non-U.S. shareholder non-U.S. shareholder non-U.S. shareholders Non-U.S. Shareholders 
 46




---



##### 



Non-U.S. Shareholders  Non-U.S. shareholders
  Information
    Reporting and Backup Withholding Tax Applicable to
    Shareholders
  U.S.
    Shareholders  Generally
              U.S.
    Shareholders  Legislation Relating To Foreign
    Accounts
  Non-U.S. Shareholders 
  Non-U.S.
    Shareholders  Generally
  non-U.S. shareholders, non-U.S. shareholder non-U.S. status non-U.S. shareholder
 47




---



##### 



non-U.S. shareholders
  non-U.S. shareholder non-U.S. shareholders non-U.S. shareholders
  non-U.S. shareholders Non-U.S. shareholders
  Non-U.S.
    Shareholders  Withholding on Payments to Certain
    Foreign Entities
  non-U.S. entities U.S.-owned
  Sunset of
    Reduced Tax Rate Provisions
    Legislative
    or Other Actions Affecting REITs
   48




---



##### 



State,
    Local and Foreign Taxes
  and/or
  Tax
    Shelter Reporting
   49




---



##### 



BOOK-ENTRY
    SECURITIES             50




---



##### 



51




---



##### 



PLAN OF
    DISTRIBUTION      over-the-counter
           52




---



##### 



over-the-counter
 53




---



##### 



LEGAL
    MATTERS   EXPERTS   WHERE TO
    FIND ADDITIONAL INFORMATION  Form S-3,
  1-800-SEC-0300. (http://www.sec.gov), http://www.first-potomac.com
   54




---



##### 



INCORPORATION
    OF CERTAIN INFORMATION BY REFERENCE    
    our Annual Report on
    Form 10-K
    for the year ended December 31, 2010;
    our Quarterly Report on
    Form 10-Q
    for the quarter ended March 31, 2011;  
    our Current Reports on
    Form 8-K
    filed with the SEC on January 11, 2011, January 14,
    2011, January 19, 2011, January 28, 2011,
    February 28, 2011, March 29, 2011, May 13, 2011,
    May 23, 2011, June 13, 2011, June 22, 2011 and
    July 1, 2011; and  
    our Registration Statement on
    Form 8-A,
    which incorporates by reference the description of our common
    shares from our Registration Statement on
    Form S-11
    (Reg.
    No. 333-107172),
    and all amendments, prospectuses or reports filed for the
    purpose of updating such description.  Form 8-K Form 10-K, Form 10-Q Form 8-K,
    First
    Potomac Realty Trust
    7600 Wisconsin Avenue
    Bethesda, Maryland 20814(301) 986-9200
  http://www.first-potomac.com
 55




---



##### 



PART II.
    INFORMATION NOT REQUIRED IN PROSPECTUS
  ITEM 14.
    OTHER
    EXPENSES OF ISSUANCE AND DISTRIBUTION.    SEC Registration Fee

$
*Accountants Fees and Expenses


**Legal Fees and Expenses


**Printing Expenses


**Miscellaneous


**TOTAL

$
**     *
    
    In accordance with Rules 456(b) and 457(r) under the
    Securities Act of 1933, the registrant is deferring payment of
    all of the registration fee.**
    
    These fees and expenses are calculated based on the number of
    issuances and amount of securities offered and accordingly
    cannot be estimated at this time.  ITEM 15.
    INDEMNIFICATION
    OF TRUSTEES AND OFFICERS.      
    the act or omission of the director or officer was material to
    the matter giving rise to the proceeding and (1) was
    committed in bad faith or (2) was the result of active and
    deliberate dishonesty;
    the director or officer actually received an improper personal
    benefit in money, property or services; or
    in the case of any criminal proceeding, the director or officer
    had reasonable cause to believe that the act or omission was
    unlawful.      
    a written affirmation by such director or officer of his or her
    good faith belief that he or she has met the standard of conduct
    necessary for indemnification by the corporation; and II-1




---



##### 




    a written undertaking by such director or officer or on such
    directors or officers behalf to repay the amount
    paid or reimbursed by the corporation if it is ultimately
    determined that the director did not meet the standard of
    conduct.    
    any present or former trustee, officer or shareholder (including
    any individual who while a trustee or officer and at our
    request, serves or has served another corporation, partnership,
    joint venture, trust, employee benefit plan or any other
    enterprise as a director, officer, partner or trustee), who has
    been successful, on the merits or otherwise, against reasonable
    expenses incurred by such person in the defense of a proceeding
    to which the trustee, officer or shareholder was made a party by
    reason of such status;
    any present or former trustee or officer against any claim or
    liability to which such trustee or officer may become subject by
    reason of such status; and
    any present or former shareholder against any claim or liability
    to which such person may become subject by reason of such
    persons status as a present or former shareholder.      ITEM 16.
    EXHIBITS.    ITEM 17.
    UNDERTAKINGS.         II-2




---



##### 



provided however
          Provided however
         II-3




---



##### 



II-4




---



##### 



SIGNATURES
  Form S-3
  FIRST POTOMAC REALTY TRUST
  By:
    /s/  Douglas
    J. Donatelli         /s/  Douglas
    J. DonatelliDouglas
    J. Donatelli

Chairman of the Board of Trustees and Chief Executive Officer
    (Principal Executive Officer)

July 1, 2011/s/  Barry
    H. BassBarry
    H. Bass

Executive Vice President and 
    Chief Financial Officer
    (Principal Financial Officer)

July 1, 2011/s/  Michael
    H. ComerMichael
    H. Comer

Senior Vice President and Chief
    Accounting Officer
    (Principal Accounting Officer)

July 1, 2011/s/  Robert
    H. ArnoldRobert
    H. Arnold

Trustee

July 1, 2011Richard
    B. Chess

TrusteeJ.
    Roderick Heller, III

Trustee/s/  R.
    Michael McCulloughR.
    Michael McCullough

Trustee

July 1, 2011/s/  Alan
    G. MertenAlan
    G. Merten

Trustee

July 1, 2011Terry
    L. Stevens

Trustee  II-5




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##### 



EXHIBIT INDEX
  Exhibit No.

Description1
.1*

Form of Common Shares Underwriting Agreement1
.2*

Form of Preferred Shares Underwriting Agreement1
.3*

Form of Depositary Shares Underwriting Agreement1
.4*

Form of Warrants Underwriting Agreement1
.5*

Form of Rights Underwriting Agreement3
.1

Amended and Restated Declaration of the Company (incorporated by
    reference to Exhibit 3.1 to the Companys Registration
    Statement on Form S-11/A (Registration No. 333-107172) filed
    with the SEC on October 1, 2003)3
.2

Articles Supplementary designating the Companys 7.750%
    Series A Cumulative Redeemable Perpetual Preferred Shares,
    liquidation preference $25.00 per share, par value $0.001 per
    share (incorporated by reference to Exhibit 3.2 to the
    Companys Registration Statement on Form 8-A (Registration
    No. 001-31824) filed with the SEC on January 18, 2011)3
.3

Form of share certificate evidencing the Companys Common
    Shares (incorporated by reference to Exhibit 4.1 to our
    Registration Statement on Form S-3 filed on November 30, 2004
    (Registration No. 333-120821))3
.4

Amended and Restated Bylaws of the Company (incorporated by
    reference to Exhibit 3.1 to the Companys Registration
    Statement on Form S-11/A (Registration No. 333-107172) filed
    with the SEC on October 1, 2003)4
.1*

Form of Deposit Agreement for Depositary Shares4
.2*

Form of Equity Warrant Agreement4
.3*

Form of Rights Agreement5
.1**

Opinion of Hogan Lovells US LLP regarding the legality of the
    securities being registered8
.1**

Opinion of Hogan Lovells US LLP regarding certain tax matters12
.1**

Computation of Ratio of Earnings to Combined Fixed Charges and
    Preferred Share Dividends23
.1**

Consent of KPMG LLP23
.2**

Consent of Hogan Lovells US LLP (included in Exhibit 5.1)23
.3**

Consent of Hogan Lovells US LLP (included in Exhibit 8.1)24
.1**

Power of Attorney (included on signature page)     *
    
    To be filed by amendment or incorporated by reference in
    connection with the offering of specific securities.**
    
    Filed herewith.