<PAGE>
                                                                   EXHIBIT 10.43





                             CONTRIBUTION AGREEMENT
                          (FUTURE MEMBERSHIP INTERESTS)




                                 BY AND BETWEEN




                    CARR CAPITAL REAL ESTATE INVESTMENTS, LLC
                      A VIRGINIA LIMITED LIABILITY COMPANY,

                                 AS CONTRIBUTOR



                                       AND



                              COLUMBIA EQUITY, LP,
                         A VIRGINIA LIMITED PARTNERSHIP,

                                   AS ACQUIRER



<PAGE>



                                TABLE OF CONTENTS

<TABLE>
<S>                 <C>                                                                                          <C>
ARTICLE I  THE CONTRIBUTION.......................................................................................1

         1.1        Contribution of Interests.....................................................................1
         1.2        Consideration.................................................................................1
         1.3        Redemption Rights for Units...................................................................2
         1.4        Tax Consequences to Contributor...............................................................2

ARTICLE II  REPRESENTATIONS AND COVENANTS.........................................................................2

         2.1        Representations by Acquirer...................................................................2
         2.2        Representations by Contributor................................................................3
         2.3        Covenants of Acquirer.........................................................................5
         2.4        Covenants of Contributor......................................................................6

ARTICLE III  Conditions Precedent to the Closing..................................................................7

         3.1        Conditions to Acquirer's Obligations..........................................................7
         3.2        Conditions to Contributor's Obligations.......................................................7

ARTICLE IV  Closing and Closing Documents.........................................................................8

         4.1        Closing.......................................................................................8
         4.2        Contributor's Deliveries......................................................................8
         4.3        Acquirer's Deliveries.........................................................................8
         4.4        Fees and Expenses; Closing Costs..............................................................9
         4.5        Adjustments...................................................................................9

ARTICLE V  Miscellaneous..........................................................................................9

         5.1        Notices.......................................................................................9
         5.2        Entire Agreement; Modifications and Waivers; Cumulative Remedies.............................10
         5.3        Exhibits.....................................................................................10
         5.4        Successors and Assigns.......................................................................10
         5.5        Article Headings.............................................................................10
         5.6        Governing Law................................................................................10
         5.7        Counterparts.................................................................................11
         5.8        Survival.....................................................................................11
         5.9        Severability.................................................................................11
         5.10       Attorneys' Fees..............................................................................11

EXHIBITS

         A        Assignment and Assumption Agreement
</TABLE>


<PAGE>


                             CONTRIBUTION AGREEMENT

         THIS CONTRIBUTION AGREEMENT (this "Agreement") is made as of this 7th
day of January, 2005 by and between Carr Capital Real Estate Investments, LLC, a
Virginia limited liability company ("Contributor"); and Columbia Equity, LP, a
Virginia limited partnership ("Acquirer").

                                    RECITALS

         A.       Carr Capital Corporation, a District of Columbia corporation
("CCC") intends to sponsor a publicly-owned real estate investment trust (the
"REIT"), which REIT will own property and membership interests in entities with
direct or indirect ownership over various real properties and improvements
located thereon, contributed by and purchased from Contributor and other
entities in exchange for partnership units (the "Units") in Acquirer.

         B.       Contributor desires to pledge and contribute 100% of any
ownership interests acquired by Contributor during the period between the date
first written above and the Closing Date (as defined below) in any commercial
office property ("Property") in the Greater Washington, DC market (the
"Interests") to Acquirer, on the terms and conditions hereinafter set forth.

         C.       Acquirer desires to acquire the Interests from Contributor, on
the terms and conditions hereinafter set forth.

                                    AGREEMENT

         NOW, THEREFORE, for and in consideration of the mutual covenants herein
contained, the parties hereto agree as follows:

                                   ARTICLE I
                                THE CONTRIBUTION

         1.1      Contribution of Interests. Contributor agrees to contribute,
transfer, assign and convey the Interests to Acquirer, and Acquirer agrees to
acquire and accept transfer of the Interests pursuant to the terms and
conditions set forth in this Agreement. The Interests shall be transferred to
Acquirer free and clear of all liens, encumbrances, security interests, prior
assignments or conveyances, conditions, restrictions, voting agreements, claims,
and any other matters affecting title thereto.

         1.2      Consideration. The total consideration (the "Consideration")
for which Contributor agrees to contribute and assign the Interests to Acquirer,
and which Acquirer agrees to pay or deliver to Contributor, subject to the terms
of this Agreement, shall be the issuance to Contributor of a number of Units
equal to (a) the Contributor's actual cash investment in the Interests, plus a
rate of return calculated on such investment from the date it is made until the
Closing Date at the Libor Rate (as defined below), (b) divided by the price per
share at which the common stock, $.001 par value per share, (the "Common Stock")
of the REIT, is offered to the public in the underwritten initial public
offering of the Common Stock (the "IPO"). The term "Libor Rate" shall mean (a)
the rate described as the "London Interbank Offered Rate" for one month in the
Money Rates section of the Wall Street Journal, determined on the Closing Date,
plus (b) eight hundred (800) basis points. On the Closing Date, the Units shall
be issued to Contributor. Upon the request of

                                     - 1 -
<PAGE>

Contributor, Acquirer shall issue certificates reflecting Contributor's
ownership of Units. The certificates evidencing the Units will bear appropriate
legends indicating (i) that the Units have not been registered under the
Securities Act of 1933, as amended ("Securities Act"), and (ii) that Acquirer's
Amended and Restated Agreement of Limited Partnership (the "Partnership
Agreement") restricts the transfer of the Units. Upon receipt of the Units and
execution and delivery of the Partnership Agreement, Contributor shall become a
limited partner of Acquirer.

         1.3      Redemption Rights for Units. Each Unit shall be redeemable, at
the option of the holder, in accordance with, but subject to the restrictions
contained in, the Partnership Agreement; provided, however, that such redemption
option may not be exercised prior to the first anniversary of the Closing Date.

         1.4      Tax Consequences to Contributor. Notwithstanding anything to
the contrary contained in this Agreement, including without limitation the use
of words and phrases such as "sell," "sale," purchase," and "pay," the parties
hereto acknowledge and agree that it is their intent that the transaction
contemplated hereby be treated for federal income tax purposes as the
contribution of the Interests by Contributor to Acquirer in exchange for Units
pursuant to Section 721 of the Internal Revenue Code of 1986, as amended (the
"Code"), and not as a transaction in which Contributor is acting other than in
its capacity as a prospective partner of Acquirer.

                                   ARTICLE II
                          REPRESENTATIONS AND COVENANTS

         2.1      Representations by Acquirer. Acquirer hereby represents and
warrants unto Contributor that the following statements are true, correct, and
complete in every material respect as of the date of this Agreement and will be
true, correct, and complete as of the Closing Date:

                  (a)      Organization and Power. Acquirer is duly organized
and validly existing, under the laws of the Commonwealth of Virginia, and has
full right, power, and authority to enter into this Agreement and to perform all
of its obligations under this Agreement; and, the execution and delivery of this
Agreement and the performance by Acquirer of its obligations under this
Agreement have been duly authorized by all requisite action of Acquirer and
require no further action or approval of Acquirer's partners or of any other
individuals or entities in order to constitute this Agreement as a binding and
enforceable obligation of Acquirer.

                  (b)      Noncontravention. Neither the entry into nor the
performance of, or compliance with, this Agreement by Acquirer has resulted, or
will result, in any violation of, or default under, or result in the
acceleration of, any obligation under the Partnership Agreement, or any
mortgage, indenture, lien agreement, note, contract, permit, judgment, decree,
order, restrictive covenant, statute, rule, or regulation applicable to
Acquirer.

                  (c)      Litigation. There is no action, suit, or proceeding,
pending or known to be threatened, against or affecting Acquirer in any court or
before any arbitrator or before any federal, state, municipal, or other
governmental department, commission, board, bureau, agency or instrumentality
which (i) in any manner raises any question affecting the validity or
enforceability of this Agreement, (ii) would reasonably be expected to
materially and adversely

                                     - 2 -
<PAGE>

affect the business, financial position, or results of operations of Acquirer,
or (iii) would reasonably be expected to materially and adversely affect the
ability of Acquirer to perform its obligations hereunder, or under any document
to be delivered pursuant hereto.

                  (d)      Units Validly Issued. The Units, when issued, will
have been duly and validly authorized and issued, free of any preemptive or
similar rights, and will be fully paid and nonassessable, without any obligation
to restore capital except as required by the Virginia Revised Uniform Limited
Partnership Act (the "Limited Partnership Act"). Upon execution and delivery of
the Partnership Agreement by Contributor, Contributor shall be admitted as a
limited partner of Acquirer as of the Closing Date and shall be entitled to all
of the rights and protections of a limited partner under the Limited Partnership
Act and the provisions of the Partnership Agreement, with the same rights,
preferences, and privileges as all other limited partners on a pari passu basis.

                  (e)      Consents. Each consent, approval, authorization,
order, license, certificate, permit, registration, designation, or filing by or
with any governmental agency or body necessary for the execution, delivery, and
performance of this Agreement or the transactions contemplated hereby by
Acquirer has been obtained.

                  (f)      Bankruptcy with respect to Acquirer. No Act of
Bankruptcy has occurred with respect to Acquirer. As used herein, "Act of
Bankruptcy" shall mean if a party hereto shall (A) apply for or consent to the
appointment of, or the taking of possession by, a receiver, custodian, trustee
or liquidator of itself or of all or a substantial part of its property, (B)
admit in writing its inability to pay its debts as they become due, (C) make a
general assignment for the benefit of its creditors, (D) file a voluntary
petition or commence a voluntary case or proceeding under the Federal Bankruptcy
Code (as now or hereafter in effect), (E) be adjudicated bankrupt or insolvent,
(F) file a petition seeking to take advantage of any other law relating to
bankruptcy, insolvency, reorganization, winding-up or composition or adjustment
of debts, (G) fail to controvert in a timely and appropriate manner, or
acquiesce in writing to, any petition filed against it in an involuntary case or
proceeding under the Federal Bankruptcy Code (as now or hereafter in effect), or
(H) take any action for the purpose of effecting any of the foregoing.

                  (g)      Brokerage Commission. Acquirer has not engaged the
services of, nor has it or will it or Contributor become liable to, any real
estate agent, broker, finder or any other person or entity for any brokerage or
finder's fee, commission or other amount with respect to the transactions
described herein on account of any action by Acquirer. Acquirer hereby agrees to
indemnify and hold Contributor and its employees, directors, members, partners,
affiliates and agents harmless against any claims, liabilities, damages or
expenses arising out of a breach of the foregoing. This indemnification shall
survive Closing or any termination of this Agreement.

         2.2      Representations by Contributor. Contributor hereby represents
and warrants unto Acquirer that each and every one of the following statements
is true, correct, and complete in every material respect as of the date of this
Agreement and will be true, correct, and complete as of the Closing Date:

                  (a)      Organization and Power. Contributor is duly
organized, validly existing, and in good standing as a limited liability company
under the laws of the Commonwealth of

                                     - 3 -
<PAGE>

Virginia. Contributor has full right, power, and authority to enter into this
Agreement and to assume and perform all of its obligations under this Agreement;
and the execution and delivery of this Agreement and the performance by
Contributor of its obligations hereunder have been duly authorized by all
requisite action of Contributor and require no further action or approval of
Contributor's members or managers or of any other individuals or entities in
order to constitute this Agreement as a binding and enforceable obligation of
Contributor.

                  (b)      Noncontravention. Neither the entry into nor the
performance of, or compliance with, this Agreement by Contributor has resulted,
or will result, in any violation of, or default under, or result in the
acceleration of, any obligation under any limited liability company agreement,
operating agreement, regulation, mortgage, indenture, lien agreement, note,
contract, permit, judgment, decree, order, restrictive covenant, statute, rule,
or regulation applicable to Contributor or to the Proceeds.

                  (c)      Litigation. There is no action, suit, claim, or
proceeding pending or threatened against or affecting Contributor or the
Interests in any court, or before any arbitrator, or before any federal, state,
municipal or other governmental department, commission, board, bureau, agency or
instrumentality which (A) in any manner raises any question affecting the
validity or enforceability of this Agreement, (B) would reasonably be expected
to materially and adversely affect the business, financial position or results
of operations of Contributor, (C) would reasonably be expected to materially and
adversely affect the ability of Contributor to perform its obligations
hereunder, or under any document to be delivered pursuant hereto, (D) would
reasonably be expected to create a lien on the Interests, any part thereof, or
any interest therein, or (E) would reasonably be expected to adversely affect
the Interests, any part thereof, or any interest therein.

                  (d)      Good Title. (A) Contributor will have good title to
the Interests on the Closing Date, (B) the Interests on the Closing Date will be
free and clear of all liens, encumbrances, pledges, voting agreements and
security interests whatsoever, and (C) Contributor has not granted any other
person or entity an option to purchase or a right of first refusal upon the
Interests nor are there any agreements or understandings between Contributor and
any other person or entity with respect to the disposition of the Interests.

                  (e)      No Consents. Each consent, approval, authorization,
order, license, certificate, permit, registration, designation, or filing by or
with, any governmental agency or body necessary of the execution, delivery, and
performance of this Agreement or the transactions contemplated hereby by
Contributor has been obtained or will be obtained on or before the Closing Date.

                  (f)      Securities Law Matters. (i) In acquiring the Units
and engaging in this transaction, neither Contributor nor any member or
shareholder thereof is relying upon any representations made to it by Acquirer,
or any of its partners, officers, employees, or agents that are not contained
herein. Contributor is aware of and understands the risks involved in investing
in the Units and in the Common Stock issuable upon redemption of such Units.
Contributor has had an opportunity to ask questions of, and to receive answers
from, Acquirer and the REIT or a person or persons authorized to act on their
behalf, concerning the terms and conditions of an investment in the Units and
the financial condition, affairs, and business of Acquirer and the

                                     - 4 -
<PAGE>

REIT. Contributor confirms that all documents, records, and information
pertaining to its investment in Acquirer that have been requested by it, have
been made available or delivered to Contributor prior to the date hereof.

                           (ii)     Contributor understands that neither
the Units nor the Common Stock issuable upon redemption of the Units have been
registered under the Securities Act or any state securities acts and are instead
being offered and sold in reliance on an exemption from such registration
requirements. The Units issuable to Contributor are being acquired solely for
its own account, for investment, and are not being acquired with a view to, or
for resale in connection with, any distribution, subdivision, or
fractionalization thereof, in violation of such laws, and Contributor does not
have any present intention to enter into any contract, undertaking, agreement,
or arrangement with respect to any such resale. Contributor understands that any
certificates representing the Units will contain appropriate legends reflecting
the requirement that the Units not be resold by Contributor without registration
under such laws or the availability of an exemption from such registration.

                  (g)      Accredited Investors. Contributor is an accredited
investor as that term is defined in Rule 501 of Regulation D under the
Securities Act of 1933, as amended.

                  (h)      Tax Matters. Contributor represents and warrants that
it has obtained from its own counsel advice regarding the tax consequences of
(i) the transfer of the Interests to Acquirer and the receipt of Units as
consideration therefor, (ii) Contributor's admission as a partner of Acquirer,
and (iii) any other transaction contemplated by this Agreement. Contributor
further represents and warrants that it has not relied on Acquirer or Acquirer's
representatives or counsel for such tax advice.

                  (i)      Bankruptcy with respect to Contributor. No Act of
Bankruptcy has occurred with respect to Contributor.

                  (j)      Brokerage Commission. Contributor has not engaged the
services of, nor has it or will it or Acquirer become liable to, any real estate
agent, broker, finder or any other person or entity for any brokerage or
finder's fee, commission or other amount with respect to the transactions
described herein on account of any action by Contributor. Contributor hereby
agrees to indemnify and hold Acquirer and its employees, directors, members,
partners, affiliates and agents harmless against any claims, liabilities,
damages or expenses arising out of a breach of the foregoing. This
indemnification shall survive Closing or any termination of this Agreement.

         2.3      Covenants of Acquirer.  Acquirer agrees as follows:

                  (a)      Further Acts. In addition to the acts, instruments
and agreements recited herein and contemplated to be performed, executed and
delivered by Acquirer and Contributor, Acquirer shall perform, execute, and
deliver or cause to be performed, executed, and delivered at the Closing or
after the Closing, any and all further acts, instruments, and agreements and
provide such further assurances as Contributor may reasonably require to
consummate the transactions contemplated hereunder.

         2.4      Covenants of Contributor.  Contributor agrees as follows:


                                     - 5 -
<PAGE>

                  (a)      Actions Regarding Interests. Except as otherwise
permitted hereby, from the date hereof until the Closing Date, Contributor shall
use reasonable commercial efforts not to take any action or fail to take any
action within Contributor's control the result of which would (1) have a
material adverse effect on the Interests, any Property, Contributor's ability to
contribute, transfer, assign and convey the Interests to Acquirer or Acquirer's
ability to continue the ownership and operation thereof after the Closing Date
in substantially the same manner as presently conducted or (2) cause any of the
representations and warranties contained in Section 2.2 to be untrue as of the
Closing Date.

                  (b)      Confidentiality. Contributor acknowledges that the
matters relating to the REIT, the IPO, this Agreement, and the other documents,
terms, conditions and information related thereto (collectively, the
"Information") are confidential in nature. Therefore, Contributor covenants and
agrees to keep the Information confidential and will not (except as required by
applicable law, regulation or legal process, and only after compliance with the
provisions of this Section 2.4) prior to the IPO, without Acquirer's prior
written consent, disclose any Information in any manner whatsoever; provided,
however, that the Information may be revealed only to Contributor's employees,
legal counsel and financial advisors, each of whom shall be informed of the
confidential nature of the Information. In the event that Contributor or its key
employees, legal counsel or financial advisors (collectively, the "Information
Group") are requested pursuant to, or required by, applicable law, regulation or
legal process to disclose any of the Information, the applicable member of the
Information Group will notify Acquirer promptly so that it may seek a protective
order or other appropriate remedy or, in its sole discretion, waive compliance
with the terms of this Section 2.4. Contributor acknowledges that remedies at
law may be inadequate to protect Acquirer or the REIT against any actual or
threatened breach of this Section 2.4, and, without prejudice to any other
rights and remedies otherwise available, Contributor agrees to the granting of
injunctive relief in favor of the REIT and/or Acquirer without proof of actual
damages. Notwithstanding any other express or implied agreement to the contrary,
the parties agree and acknowledge that each of them and each of their employees,
representatives, and other agents may disclose to any and all persons, without
limitation of any kind, the tax treatment and tax structure of the transaction
and all materials of any kind (including opinions or other tax analyses) that
are provided to any of them relating to such tax treatment and tax structure,
except to the extent that confidentiality is reasonably necessary to comply with
U.S. federal or state securities laws. For purposes of this paragraph, the terms
"tax treatment" and "tax structure" have the meanings specified in Treasury
Regulation section 1.6011-4(c).

                  (c)      Further Acts. In addition to the acts, instruments
and agreements recited herein and contemplated to be performed, executed and
delivered by Acquirer and Contributor, Contributor shall perform, execute, and
deliver or cause to be performed, executed, and delivered at the Closing or
after the Closing, any and all further acts, instruments, and agreements and
provide such further assurances as Acquirer may reasonably require to consummate
the transactions contemplated hereunder.


                                     - 6 -
<PAGE>

                                  ARTICLE III
                       CONDITIONS PRECEDENT TO THE CLOSING

         3.1      Conditions to Acquirer's Obligations. In addition to any other
conditions set forth in this Agreement, Acquirer's obligation to consummate the
Closing is subject to the timely satisfaction of each and every one of the
conditions and requirements set forth in this Section 3.1, all of which shall be
conditions precedent to Acquirer's obligations under this Agreement.

                  (a)      Contributor's Obligations. Contributor shall have
performed all obligations of Contributor hereunder which are to be performed
prior to Closing, and shall have delivered or caused to be delivered to
Acquirer, all of the documents and other information required of Contributor
pursuant to Section 4.2.

                  (b)      Contributor's Representations and Warranties.
Contributor's representations and warranties set forth in Section 2.2 shall be
true and correct in all material respects as if made again on the Closing Date,
and Contributor shall have executed and delivered to Acquirer at Closing a
certificate to the foregoing effect.

                  (c)      No Injunction. On the Closing Date, there shall be no
effective injunction, writ, preliminary restraining order or other order issued
by a court of competent jurisdiction restraining or prohibiting the consummation
of the transactions contemplated hereby.

                  (d)      Completion of IPO.  The IPO shall have been
completed.

                  (e)      Closing.  The Closing shall have occurred on or prior
to June 30, 2005.

         3.2      Conditions to Contributor's Obligations. In addition to any
other conditions set forth in this Agreement, Contributor's obligation to
consummate the Closing is subject to the timely satisfaction of each and every
one of the conditions and requirements set forth in this Section 3.2, all of
which shall be conditions precedent to Contributor's obligations under this
Agreement.

                  (a)      Acquirer's Obligations. Acquirer shall have performed
all obligations of Acquirer hereunder which are to be performed prior to
Closing, and shall have delivered or caused to be delivered to Contributor, all
of the documents and other information required of Acquirer pursuant to Section
4.3.

                  (b)      Acquirer's Representations and Warranties. Acquirer's
representations and warranties set forth in Section 2.1 shall be true and
correct in all material respects as if made again on the Closing Date, and
Acquirer shall have executed and delivered to Contributor at Closing a
certificate to the foregoing effect.

                  (c)      No Injunction. On the Closing Date, there shall be no
effective injunction, writ, preliminary restraining order or other order issued
by a court of competent jurisdiction restraining or prohibiting the consummation
of the transactions contemplated hereby.

                  (d)      Completion of IPO.  The IPO shall have been
completed.

                                     - 7 -
<PAGE>

                  (e)      Closing.  The Closing shall have occurred on or prior
to June 30, 2005.

                                   ARTICLE IV
                          CLOSING AND CLOSING DOCUMENTS

         4.1      Closing. The consummation and closing (the "Closing") of the
transactions contemplated under this Agreement shall take place at the offices
of Hunton & Williams LLP, Washington, D.C., or such other place as is mutually
agreeable to the parties, on the date of the closing of the IPO (the "Closing
Date"), or as otherwise set by agreement of the parties; provided, however, that
this Agreement shall terminate if Closing does not occur prior to June 30, 2005.

         4.2      Contributor's Deliveries. At the Closing, Contributor shall
deliver the following to Acquirer in addition to all other items required to be
delivered to Acquirer by Contributor:

                  (a)      Assignment of Interests. Contributor shall have
executed and delivered to Acquirer an Assignment and Assumption Agreement, in
substantially the form of Exhibit A attached hereto (the "Assignment and
Assumption Agreement");


                  (b)      Execution of Partnership Agreement. The Signature
page of the Partnership Agreement duly executed by Contributor as a limited
partner; and

                  (c)      Authority Documents. Evidence satisfactory to
Acquirer that the person or persons executing the closing documents on behalf of
Contributor has full right, power, and authority to do so.

                  (d)      FIRPTA Certificate. An affidavit from Contributor
certifying pursuant to Section 1445 of the Internal Revenue Code that
Contributor is not a foreign corporation, foreign partnership, foreign trust,
foreign estate or foreign person (as those terms are defined in the Internal
Revenue Code and the Income Tax Regulations promulgated thereunder), in form and
substance satisfactory to Acquirer.

                  (e)      Certificate of Representations and Warranties. The
certificate required by Section 3.1(b).

                  (f)      Other Documents. Any other document or instrument
reasonably requested by Acquirer or required hereby.

         4.3      Acquirer's Deliveries. At the Closing, Acquirer shall deliver
the following to Contributor:

                  (a)      Certificates for Units. If certificates are issued,
certificates duly issued by Acquirer in the name of Contributor as of the
Closing Date representing the Units to which Contributor is entitled pursuant to
Section 1.2 of this Agreement;

                  (b)      Assumption of Interests. Acquirer shall have executed
and delivered to Contributor an Assignment and Assumption Agreement.


                                     - 8 -
<PAGE>

                  (c)      Executed Partnership Agreement. An original of the
Partnership Agreement, duly executed by its general partner; and

                  (d)      Authority Documents. Evidence satisfactory to
Contributor that the person or persons executing the closing documents on behalf
of Acquirer have full right, power, and authority to do so.

                  (e)      Certificate of Representations and Warranties. The
certificate required by Section 3.2(b).

                  (f)      Other Documents. Any other document or instrument
reasonably requested by Contributor or required hereby.

         4.4      Fees and Expenses; Closing Costs. Acquirer shall pay all fees,
expenses and closing costs relating to the transactions contemplated by this
Agreement; provided however, that Contributor shall pay its own attorneys' and
consultants' fees and expenses.

         4.5      Adjustments. Acquirer shall deliver the number Units, whether
certificated or otherwise, to which Contributor is entitled pursuant to Section
1.2 of this Agreement without any setoffs or adjustments.


                                   ARTICLE V
                                  MISCELLANEOUS

         5.1      Notices. Any notice provided for by this Agreement and any
other notice, demand, or communication required hereunder shall be in writing
and either delivered in person (including by confirmed facsimile transmission)
or sent by registered or certified mail or overnight courier, return receipt
requested, in a sealed envelope, postage prepaid, and addressed to the party for
which such notice, demand or communication is intended at such party's address
as set forth in this Section. All notices to Acquirer shall be addressed as
follows:

         ACQUIRER:

                  Columbia Equity, LP
                  c/o Carr Capital Corporation
                  1750 H Street, NW, Suite 500
                  Washington, DC  20005
                  Telephone:  (202) 303-3060
                  Facsimile:  (202) 303-3078
                  Attn:  Oliver T. Carr, III

Contributor's address for all purposes under this Agreement shall be the
following:


                                     - 9 -
<PAGE>

         CONTRIBUTOR:

                  Carr Capital Real Estate Investments, LLC
                  c/o Carr Capital Corporation
                  1750 H Street, NW, Suite 500
                  Washington, DC  20005

Any address or name specified above may be changed by a notice given by the
addressee to the other party. Any notice, demand or other communication shall be
deemed given and effective as of the date of delivery in person or receipt set
forth on the return receipt. The inability to deliver because of changed address
of which no notice was given, or rejection or other refusal to accept any
notice, demand or other communication, shall be deemed to be receipt of the
notice, demand or other communication as of the date of such attempt to deliver
or rejection or refusal to accept.

         5.2      Entire Agreement; Modifications and Waivers; Cumulative
Remedies. This Agreement supersedes any existing letter of intent between the
parties, constitutes the entire agreement among the parties hereto and may not
be modified or amended except by instrument in writing signed by the parties
hereto, and no provisions or conditions may be waived other than by a writing
signed by the party waiving such provisions or conditions. No delay or omission
in the exercise of any right or remedy accruing to Contributor or Acquirer upon
any breach under this Agreement shall impair such right or remedy or be
construed as a waiver of any such breach theretofore or thereafter occurring.
The waiver by Contributor or Acquirer of any breach of any term, covenant, or
condition herein stated shall not be deemed to be a waiver of any other breach,
or of a subsequent breach of the same or any other term, covenant, or condition
herein contained. All rights, powers, options, or remedies afforded to
Contributor or Acquirer either hereunder or by law shall be cumulative and not
alternative, and the exercise of one right, power, option, or remedy shall not
bar other rights, powers, options, or remedies allowed herein or by law, unless
expressly provided to the contrary herein.

         5.3      Exhibits. All exhibits referred to in this Agreement and
attached hereto are hereby incorporated in this Agreement by reference.

         5.4      Successors and Assigns. Except as set forth in this Article,
this Agreement may not be assigned by Acquirer or Contributor without the prior
approval of the other party hereto. This Agreement shall be binding upon, and
inure to the benefit of, Contributor, Acquirer, and their respective legal
representatives, successors, and permitted assigns.

         5.5      Article Headings. Article headings and article and section
numbers are inserted herein only as a matter of convenience and in no way
define, limit, or prescribe the scope or intent of this Agreement or any part
hereof and shall not be considered in interpreting or construing this Agreement.

         5.6      Governing Law. This Agreement shall be construed and
interpreted in accordance with the laws of the Commonwealth of Virginia, without
regard to conflicts of laws principles.

                                     - 10 -
<PAGE>

         5.7      Counterparts. This Agreement may be executed in any number of
counterparts and by any party hereto on a separate counterpart, each of which
when so executed and delivered shall be deemed an original and all of which
taken together shall constitute but one and the same instrument.

         5.8      Survival. All representations and warranties contained in this
Agreement, and all covenants and agreements contained in the Agreement which
contemplate performance after the Closing Date shall survive the Closing.

         5.9      Severability. In case any one or more of the provisions
contained in this Agreement shall for any reason be held to be invalid, illegal,
or unenforceable in any respect, such invalidity, illegality, or
unenforceability shall not affect any other provision hereof, and this Agreement
shall be construed as if such invalid, illegal, or unenforceable provision had
never been contained herein.

         5.10     Attorneys' Fees. Should a party employ an attorney or
attorneys to enforce any of the provisions hereof or to protect its interest in
any manner arising under this Agreement, or to recover damages for breach of
this Agreement, any non-prevailing party in any action pursued in a court of
competent jurisdiction (the finality of which is not legally contested) shall
pay to the prevailing party all reasonable costs, damages, and expenses,
including reasonable attorneys' fees, expended or incurred in connection
therewith.



                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]
                      [SIGNATURES APPEAR ON FOLLOWING PAGE]


                                     - 11 -
<PAGE>

         IN WITNESS WHEREOF, this Agreement has been entered into effective as
of the date first above written.


                           CONTRIBUTOR:

                           Carr Capital Real Estate Investment, LLC, a
                           Virginia limited liability company

                                    By:  Carr Capital Corporation, a District
                                    of Columbia corporation, its managing
                                    member


                                    By:      /s/  Oliver T. Carr, III
                                       -----------------------------------------
                                    Name:  Oliver T. Carr, III
                                    Title: President & Chief Executive Officer



                           ACQUIRER:

                           Columbia Equity, LP, a Virginia limited partnership

                           By: Columbia Equity Trust, Inc., a Maryland
                               corporation, its general partner


                                    By:      /s/  Oliver T. Carr, III
                                       -----------------------------------------
                                    Name:  Oliver T. Carr, III
                                    Title: President & Chief Executive Officer



                                     - 12 -
<PAGE>


                                    EXHIBIT A

                       ASSIGNMENT AND ASSUMPTION AGREEMENT

Carr Capital Real Estate Investments, LLC, a Virginia limited liability company
("Assignor"), for good and valuable consideration paid to the Assignor by
Columbia Equity, LP, a Virginia limited partnership ("Assignee"), pursuant to
the Contribution Agreement dated as of [__________], 2005, by and between
Assignor and Assignee (the "Agreement") and for other good and valuable
consideration, the receipt and adequacy of which are hereby acknowledged, does
hereby sell, assign, transfer, convey and deliver to the Assignee, its
successors and assigns, good and indefeasible title to the membership interests
(the "Interests") in the limited liability companies (the "Limited Liability
Companies") identified on Schedule 1 attached hereto, free and clear of all
liens, encumbrances, security interests, prior assignments, conditions,
restrictions, pledges, voting agreements, claims, and other matters affecting
title thereto, subject to the operating agreements of the Limited Liability
Companies. Assignee does hereby accept the foregoing Assignment and assumes and
agrees to be responsible for all liabilities and obligations under the operating
agreements of the Limited Liability Companies from and after the date hereof
relating to the Interests.

Capitalized terms used but not defined herein shall have the respective meanings
ascribed to them in the Agreement.

IN WITNESS WHEREOF, the parties hereto have caused this Assignment and
Assumption Agreement to be signed by a duly authorized officer of each, this __
day of _______, 2005.


                            ASSIGNOR:



                            -----------------------, a

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


                            By:
                               -------------------------------------------------
                            Name:
                                 -----------------------------------------------
                            Title:
                                  ----------------------------------------------


                            ASSIGNEE:

                            Columbia Equity, LP, a Virginia limited partnership


                            By:
                               -------------------------------------------------
                            Name:
                                 -----------------------------------------------
                            Title:
                                  ----------------------------------------------