Document:

<PAGE>

                                                                   Exhibit 10.21

                                LOAN AGREEMENT

     THIS LOAN AGREEMENT ("Agreement") is made and entered into as of the 16th
day of April, 2001, between PRIMUS KNOWLEDGE SOLUTIONS, INC., a Washington
corporation ("Lender") and MICHAEL BROCHU ("Borrower").

                                   RECITALS:

     A.   Lender has agreed to make a loan (the "Loan") to Borrower in the
amount of $750,000.

     B.   This Agreement sets forth certain terms and conditions in connection
with the Loan.

                                   AGREEMENT

     NOW, THEREFORE, in consideration of the mutual covenants set forth herein,
Lender and Borrower agree as follows:

1.   THE LOAN

     1.1  Disbursements

     The funds shall be disbursed to Michael Brochu via check or by wire
transfer.

     1.2  Promissory Note

     The Loan shall be evidenced by Borrower's Promissory Note ("Note") in the
Loan amount.

     1.3  Loan Documents

     As used in this Agreement, "Loan Documents" means this Agreement and the
Note, and all other documents and instruments relating to the Loan.

2.   FURTHER ASSURANCES

     Whenever requested by Lender, Borrower shall promptly execute and deliver
to Lender such instruments and documents as Lender may reasonably require to
further evidence the Loan.

                                                                          PAGE 1
<PAGE>

3.   DEFAULT

     3.1  Event of Default

     Any one or more of the following events is an Event of Default ("Event of
Default") under this Agreement.

     (a)  There is an Event of Default as defined under any of the other Loan
Documents.

     (b)  Borrower fails to pay any installment of principal or interest on the
Note, within five days of the date due, whether at scheduled maturity, by
acceleration, or otherwise.

     (c)  Borrower shall file a voluntary petition in bankruptcy or such a
petition shall be filed against Borrower and is not dismissed within 60 days
after filing; or if Borrower shall file any petition or answer seeking or
acquiescing in any reorganization, arrangement, composition, readjustment,
liquidation, dissolution or similar relief for itself under any present or
future federal, state or other statute, law or regulation relating to
bankruptcy, insolvency or other relief for debtors; or shall make any general
assignment for the benefit of creditors, or shall admit in writing his inability
to pay his debts generally as they become due.

     (d)  A court of competent jurisdiction shall enter an order, judgment or
decree approving a petition filed against Borrower seeking any reorganization,
dissolution or similar relief under any present or future federal, state or
other statute, law or regulation relating to bankruptcy, insolvency or other
relief for debtors and such order, judgment or decree shall remain unvacated and
unstayed for an aggregate of 60 days (whether or not consecutive) from the first
date of entry thereof.

     (e)  Borrower fails to perform or comply with any obligation, covenant,
or other term of this Agreement or the Note, and that default is not rectified
within 14 days.

     (f)  The death of Borrower.

     (g)  Termination of Borrower's employment with Lender for any reason other
than without Cause or for Good Reason following a Change of Control (as defined
in Section 5.1 below).

     3.2  Inapplicability of Cure Periods

     All cure periods provided in this Agreement shall be inapplicable if, in
Lender's reasonable judgment, the default is not capable of being cured within
the time allowed.

     3.3  Forgiveness of Note

     Upon the Termination of Borrower's employment with Lender without Cause or
for Good Reason following a Change of Control, the entire principal amount plus
all accrued

                                                                          PAGE 2
<PAGE>

interest under the Note shall be forgiven Borrower and the Note shall be of no
further force or effect. Borrower acknowledges that he has had opportunity to
discuss the possible tax consequences of such forgiveness of indebtedness with
his legal and/or tax advisors and accepts full responsibility for any adverse
tax consequences flowing therefrom.

4.   REMEDIES

     4.1  Acceleration

     Upon the occurrence of an Event of Default, the entire amount disbursed
under the Note is immediately due and payable at the election of Lender,
provided, however, that in the event of a Default pursuant to Section 3.1(h),
the Note, together with all accrued interest thereunder, shall be due ninety
(90) days after the date of such Default.

     4.2  Remedies Not Exclusive

     No remedy conferred upon or reserved to Lender in the Loan Documents shall
be exclusive of any other remedy provided in the Loan Documents or by law or in
equity, and each shall be cumulative and shall be in addition to every other
remedy given Lender under any of the Loan Documents or now or hereafter existing
at law or in equity or by statute.  Lender at its sole option, without limiting
or affecting any rights and remedies hereunder, may exercise any of the rights
and remedies to which it may be entitled under the Loan Documents concurrently
or in such order as Lender may determine.  The exercise of any rights of Lender
shall not in any way constitute a cure or waiver of an Event of Default or
invalidate any act done pursuant to any notice of default or prejudice Lender in
the exercise of any of its rights.  No failure of Lender to enforce its rights,
remedies, or options shall be deemed to be a waiver of any such rights, remedies
or options.

5.   MISCELLANEOUS

     5.1  Definitions

     The terms "Change of Control," "Cause," and "Good Reason" shall have the
meanings assigned to such terms in that certain Change of Control Agreement
dated as of June 30, 1999 between Borrower and Lender.  All other terms shall
have the meaning ascribed to such terms herein.

     5.2  Assignment

     Borrower may not assign his rights under this Agreement or any of the
Loan Documents without the prior written consent of Lender.

     5.3  Notices

     (a)  All notices, requests, consents, approvals, waivers and other
communications shall be in writing and mailed, faxed or delivered to the address
or facsimile number

                                                                          PAGE 3
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specified below (provided, however, that any matter transmitted to the Lender by
facsimile (i) shall be promptly confirmed by a telephone call to the Lender at
the number specified below and (ii) shall be followed promptly by delivery of a
hard copy original thereof) or to such other address or facsimile number as
shall be designated by a party in a written notice to the other party.

               If to Lender:

               Primus Knowledge Solutions, Inc.
               1601 Fifth Avenue, Suite 1900
               Seattle, Washington 98101
               Attention: Dave Williamson
               Facsimile No. (206) 834-8111
               Telephone No. (206) 834-8452

               If to Borrower:

               Michael Brochu
               at his home address and telephone number on the Lender's records

     (b)  All such notices, requests and communications shall, when transmitted
by overnight delivery, or faxed, be effective when delivered for overnight
(next-day) delivery, or transmitted in legible form by facsimile machine,
respectively, or if mailed, upon receipt by the addressee, or if delivered, upon
delivery.

     5.4  Third Parties

     No provision of this Agreement is intended or shall be construed to be for
the benefit of any third party.

     5.5  Captions

     All section or paragraph division, numbering, and captions are for
convenience of reference only, and shall not affect the interpretation or
construction of this Agreement or of any term, condition, or provision hereof.

     5.6  Entire Agreement; Modifications

     This Agreement and the Loan Documents constitute the entire agreement of
the parties and supersede all prior negotiations, agreements or understandings
and may not be contradicted by evidence of any alleged oral agreement.  No
modification or amendment of this Agreement or the Loan Documents shall be
effective unless set forth in writing and signed by Lender and Borrower.

                                                                          PAGE 4
<PAGE>

     5.7  Counterparts

     This Agreement may be executed in one or more counterparts, all of which
together shall constitute one and the same original.

     5.8  Severability

     If any term or provision of this Agreement is illegal or invalid for any
reason, such illegality or invalidity shall not affect the enforceability of the
remaining provisions of this Agreement and the other Loan Documents.

     5.9  Term

     This Agreement shall remain in effect until the Loan has been repaid in
full.

     5.10 Governing Law

     This Agreement shall be governed by the laws of the State of Washington.

     5.11 Jurisdiction

     All judicial proceedings brought against borrower arising out of or
relating to this note may be brought in any state or federal court of competent
jurisdiction in the State of Washington, and by execution and delivery of this
agreement borrower accepts for itself and in connection with its properties,
generally and unconditionally, the nonexclusive jurisdiction of the aforesaid
courts and waives any defense of forum non conveniens and irrevocably agrees to
be bound by any judgment rendered thereby in connection with this agreement.

            [The remainder of this page intentionally left blank.]

                                                                          PAGE 5
<PAGE>

     ORAL AGREEMENTS OR ORAL COMMITMENTS TO LOAN MONEY, EXTEND CREDIT, OR
FORBEAR FROM ENFORCING REPAYMENT OF A DEBT ARE NOT ENFORCEABLE UNDER WASHINGTON
LAW.

     IN WITNESS WHEREOF, the parties have signed this Agreement as of the date
written above.

                                        /s/ Michael Brochu
                                        --------------------------------------
                                        Michael Brochu

                                        PRIMUS KNOWLEDGE SOLUTIONS, INC.

                                        By: /s/ Ronald Stevens
                                           -----------------------------------
                                        Name: Ronald Stevens
                                        Title: VP and Chief Financial Officer

                                                                          PAGE 6<PAGE>

                                                                   Exhibit 10.22

                                PROMISSORY NOTE

$750,000                                                    Seattle, Washington
                                                                 April 16, 2001

     FOR VALUE RECEIVED, Michael Brochu, "Borrower"; promises to pay, in lawful
money of the United States of America, to the order of Primus Knowledge
Solutions, Inc., a Washington corporation ("Lender"), at 1601 Fifth Avenue,
Suite 1900, Seattle, WA 98101, or such other place either within or without the
State of Washington as Lender may designate in writing from time to time, the
principal sum of SEVEN HUNDRED FIFTY THOUSAND and no/100 DOLLARS ($750,000), or
so much as may be advanced hereunder, payable with interest as provided below.
The proceeds of the loan ("Loan") evidenced by this Note are to be advanced
under the terms and conditions of the Loan Agreement ("Loan Agreement") between
Lender and Borrower dated the same date as this Note.

1.   Definitions

     Except as set forth in this Note, capitalized terms shall have the meanings
given them in the Loan Agreement. For purposes of this Note, the following terms
shall have the definitions set forth below:

     "Business Day" means any day, other than Saturday, Sunday or a day on which
national banks in Seattle, Washington are authorized or required by law to be
closed.

     "Maturity Date" means April 16, 2007, unless earlier accelerated or
terminated pursuant to the terms of this Note or the Loan Agreement.

2.   Interest

     (a)  This Note shall bear simple interest at the rate of 4.94% per annum.

     (b)  All computations of interest and fees shall be based on a 360-day year
for the actual number of days elapsed.

     (c)  Notwithstanding any provision contained herein or in the Note, the
total liability of Borrower for payment of interest pursuant hereto, including
late charges, shall not exceed the maximum amount of interest permitted by
applicable law to be charged, collected or received from Borrower; and if any
payments by Borrower include interest in excess of that maximum amount, Lender
shall apply the excess first to reduce the unpaid balance of the Loan, then the
excess shall be returned to Borrower.

                                                                          PAGE 1
<PAGE>

3.   Payments

     3.1  Time and Place of Payments

     (a)  Principal and interest upon this Note shall accrue, with no payments
being due or payable hereunder until April 16, 2005.

     (b)  The principal amount and all interest accrued through and including
April 10, 2005 will be completely amortized over the fourth, fifth, and sixth
years of the term of this Note, with payments due April 16, 2005, April 16,
2006, and April 16, 2007.

     (c)  All of Borrower's obligations under this Note shall be finally due and
payable upon the Maturity Date, at which time all remaining sums due hereunder
shall be paid in full.

     (d)  All payments made hereunder shall be delivered to Lender at the
address set forth above, or at a different place required by Lender or by any
other party who takes this Note by transfer and who is entitled to receive
payment ("Holder").

     (e)  All sums payable hereunder shall be paid in immediately available
United States funds.

     (f)  Whenever any payment to be made hereunder or on the Note becomes
due and payable on a day that is not a Business Day, such payment may be made on
the next succeeding Business Day and such extension of time shall in such case
be included in computing interest on such payment.

     3.2  Application of Payments

     Payments shall be applied in the following order: (1) to the payment of
attorneys' fees and other costs of collection, if any, (2) to the payment of
late charges, if any; (3) to the payment of accrued interest, computed on a
360-day yearly basis and collected for the actual number of days in the month,
based on the outstanding principal balance to the due date; and (4) to the
reduction of the principal balance.

     3.3  Forgiveness of Note

     Notwithstanding anything in this Note to the Contrary, in the event
Borrower's employment with Lender is terminated without Cause or for Good Reason
following a Change of Control (in each case as such term is defined in that
certain Change of Control Agreement dated as of June 30, 1999 among Borrower and
Lender) all amounts owing under this Note shall be forgiven and this Note shall
be of no further force and effect. Borrower has consulted with legal and/or tax
advisors regarding the economic and tax impact such forgiveness of indebtedness
may have on Borrower and Borrower accepts the same. In the event of such a
termination, Lender will return this original Note to Borrower, or destroy the
same, at Borrower's option.

                                                                          PAGE 2
<PAGE>

4.   Prepayment

     Borrower shall have the right, at any time, to prepay the whole or any part
the principal hereof without prepayment charges. All prepayments shall be
credited first upon accrued interest and then upon the last maturing installment
of principal. If Borrower makes such a partial prepayment, there will be no
changes in the due dates of the monthly payments unless Lender agrees in writing
to those changes. When a prepayment is made by Borrower, Borrower will tell
Lender in writing that Borrower is doing so.

5.   Security

     This Note is an unsecured obligation of the Borrower.

6.   Events of Default

     The occurrence of either of the following shall constitute an "Event of
Default" under this Note: (i) the failure by Borrower to make any payment under
this Note upon the date it is due, or (ii) the occurrence of an Event of Default
as defined in the Loan Agreement.

7.   Remedies; Default Interest

     Upon the occurrence of any Event of Default, Lender may declare the entire
principal balance and all accrued interest immediately due and payable.
Notwithstanding the foregoing, in the only Event of Default is pursuant to
Section 3.1(h) of the Loan Agreement, this Note will be due and payable ninety
(90) days following the occurrence of such Event of Default. Whether or not
Lender exercises such option to accelerate upon the occurrence of any Event of
Default, the entire principal balance and all accrued interest under the Loan
and all other amounts payable under the Loan Agreement shall bear interest from
the date of the Event of Default at a default rate equal to three percent (3%)
plus the rate of interest otherwise payable under this Note. Such default
interest shall be payable on demand. Lender's failure to exercise any right or
remedy shall not be a waiver of the right to exercise the same upon any
subsequent Event of Default. The foregoing remedies shall be in addition to all
other legal and equitable rights and remedies of Lender.

8.   General

     (a)  Waivers. Except as otherwise provided in the Loan Agreement,
          -------
Borrower waives all notices required by law; including without limitation
presentment and demand for payment, protest, and notice of demand, protest,
dishonor and nonpayment.

     (b)  Costs and Attorney's Fees. Upon the occurrence of any Event of
          -------------------------
Default, Lender shall have the right, at Borrower's expense, to consult an
attorney or collection agency, to make any demand, enforce any remedy, or
otherwise protect its rights under this Note and the Loan Agreement. Borrower
hereby promises to pay all costs, fees, and expenses so incurred by Lender,
including, without limitation, reasonable attorney fees (with or without
arbitration or litigation), arbitration and court costs, collection agency
charges, notice

                                                                          PAGE 3
<PAGE>

expenses and title search expenses, and the failure of the defaulting Borrower
to pay the same shall, in itself, constitute a further and additional default.
In the event that suit or action or arbitration is instituted by Lender to
enforce this Note or any rights under the Loan Agreement, Borrower hereby
promises to pay, in addition to costs and expenses provided by statute or
otherwise, such sums as the court or arbitrator may adjudge reasonable as
attorney fees in such proceeding and on any appeals from any judgment or decree
entered therein and the reasonable costs and attorney fees for collection of the
amount due therein; provided that if either Borrower or Lender institute any
action or arbitration under the Loan Agreement or this Note, the prevailing
party in any such action or arbitration shall be entitled to such costs and
fees, including attorney fees, as the court or arbitrator may adjudge as
reasonable in such proceeding. Borrower further agrees to pay immediately upon
demand all costs and expenses of Lender including reasonable attorney fees: (i)
if Lender attempts to have any stay or injunction prohibiting the enforcement or
collection of the Note or prohibiting the enforcement of any other Loan Document
lifted by any bankruptcy or other court; (ii) if Lender participates in any
subsequent proceedings or appeal from any order or judgment entered in any such
proceeding; (iii) if Lender deems it appropriate to file a proof of claim or in
any other manner participate in any bankruptcy or similar proceedings; or (iv)
if Lender retains legal counsel in connection with any amendments or
modifications to this Note or any other Loan Document.

     (c)  Waiver of Jury Trial. BORROWER, AND LENDER BY ITS ACCEPTANCE OF THIS
          --------------------
NOTE, HEREBY AGREES TO WAIVE ITS RESPECTIVE RIGHTS TO A JURY TRIAL OF ANY CLAIM
OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF THIS NOTE OR THE LOAN AGREEMENT
OR ANY DEALINGS BETWEEN THEM RELATING TO THE SUBJECT MATTER OF THE LOAN
TRANSACTION CONTEMPLATED BY THE LOAN AGREEMENT OR THE LENDING RELATIONSHIPS THAT
ARE BEING ESTABLISHED. The scope of this waiver is intended to be all-
encompassing of any and all disputes that may be filed in any court and that
relate to the subject matter of this transaction, including without limitation,
contract claims, tort claims, breach of duty claims, and all other common law
and statutory claims. Borrower, and Lender by its acceptance of this Note,
acknowledges that this waiver is a material inducement to enter into a business
relationship, that each has already relied on this waiver in making and
accepting this Note, and that each will continue to rely on this waiver in their
related future dealings. Borrower, and Lender by its acceptance of this Note,
further warrants and represents that it has reviewed this waiver with its legal
counsel and that it knowingly and voluntarily waives its jury trial rights
following consultation with legal counsel. THIS WAIVER IS IRREVOCABLE, MEANING
THAT IT MAY NOT BE MODIFIED EITHER ORALLY OR IN WRITING, AND THIS WAIVER SHALL
APPLY TO ANY SUBSEQUENT AMENDMENTS, RENEWALS, SUPPLEMENTS, OR MODIFICATIONS TO
THIS AGREEMENT OR THE LOAN AGREEMENT OR TO ANY OTHER DOCUMENTS OR AGREEMENTS
RELATING TO THE LOAN MADE HEREUNDER. In the event of litigation, this agreement
may be filed as a written consent to a trial by the court.

                                                                          PAGE 4
<PAGE>

     (d)  Business Purpose. Borrower warrants and represents that all funds
          ----------------
advanced under this Note shall be applied to and are intended solely for
business or commercial purposes.

     (e)  Governing Law. This Note shall be construed, enforced and otherwise
          -------------
governed by the laws of the State of Washington.

     (f)  Forum. ALL JUDICIAL PROCEEDINGS BROUGHT AGAINST BORROWER ARISING
          -----
OUT OF OR RELATING TO THIS NOTE MAY BE BROUGHT IN ANY STATE OR FEDERAL COURT OF
COMPETENT JURISDICTION IN THE STATE OF WASHINGTON, AND BY EXECUTION AND DELIVERY
OF THIS AGREEMENT BORROWER ACCEPTS FOR ITSELF AND IN CONNECTION WITH ITS
PROPERTIES, GENERALLY AND UNCONDITIONALLY, THE NONEXCLUSIVE JURISDICTION OF THE
AFORESAID COURTS AND WAIVES ANY DEFENSE OF FORUM NON CONVENIENS AND IRREVOCABLY
AGREES TO BE BOUND BY ANY JUDGMENT RENDERED THEREBY IN CONNECTION WITH THIS
AGREEMENT. Borrower hereby agrees that service of process sufficient for
personal jurisdiction in any action against Borrower in the State of Washington
may be made by registered or certified mail, return receipt requested, to
Borrower at its address as provided in the Loan Agreement, and Borrower hereby
acknowledges that such service shall be effective and binding in every respect.
Nothing herein shall affect the right to serve process in any other manner
permitted by law or shall limit the right of Borrower or Lender to bring
proceedings in the courts of any other jurisdiction, or to object thereto.

     (g)  Notice. Any notice to Borrower under this Note shall be given as
          ------
provided in the Loan Agreement.

     (h)  Replacement Note. If this Note is lost, stolen, destroyed or
          ----------------
mutilated, Borrower shall execute a replacement note upon the written request of
Lender.

     (i)  Time of Essence. Time is of the essence for purposes of this Note and
          ---------------
the other Loan Agreement.

     EXCEPT AS OTHERWISE PROVIDED IN THIS NOTE OR THE LOAN DOCUMENTS, BORROWER
ACKNOWLEDGES LIABILITY FOR PAYMENT OF ALL AMOUNTS OWING UNDER THIS NOTE AND THE
LOAN AGREEMENT.

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                                                                          PAGE 5
<PAGE>

     ORAL AGREEMENTS OR ORAL COMMITMENTS TO LOAN MONEY, EXTEND CREDIT, OR
FORBEAR FROM ENFORCING REPAYMENT OF A DEBT ARE NOT ENFORCEABLE UNDER WASHINGTON
LAW.

     IN WITNESS WHEREOF, Borrower executes this Note as of the day and year
first above written.

                                   BORROWER:

                                   /s/ Michael Brochu
                                   --------------------------------
                                   Michael Brochu

                                                                          PAGE 6

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