Document:

<Page>

                                                                   EXHIBIT 10.21

                                  AMENDMENT TO
                      HOOVER'S, INC. STOCK OPTION AGREEMENT

     THIS AMENDMENT TO HOOVER'S, INC. STOCK OPTION AGREEMENT (this "AMENDMENT")
is entered into and made effective as of the 30th day of March, 2002 (the
"EFFECTIVE DATE"), by and between Hoover's, Inc., a corporation organized under
the laws of Delaware (the "CORPORATION"), and Jeffrey R. Tarr, who is an
Employee and the Chairman of the Board of Directors of the Corporation
("OPTIONEE"). Capitalized terms not otherwise defined herein shall be as set
forth in the Option Agreement, as defined below.

                                 R E C I T A L S

          WHEREAS, the Corporation entered into a Hoover's, Inc. Stock Option
Agreement dated May 22, 2001 whereby the Corporation granted Optionee an Option
(the "150,000 SHARES OPTION") under The Hoover's, Inc. 1999 Stock Incentive Plan
(the "Plan") to acquire 150,000 shares of Common Stock, $0.01 par value of the
Corporation, at an exercise price of $5.00 per share, such number of shares and
exercise price SUBJECT TO ADJUSTMENT for subsequent stock splits of the
Corporation (the "Option Agreement");

          WHEREAS, the parties desire to amend the Option Agreement to provide
that the vesting of the 150,000 Shares Option shall accelerate fully immediately
prior to a Change in Control of the Company.

          NOW, THEREFORE, in consideration of the foregoing, and the mutual
covenants and conditions herein contained, and for other valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

     1.   FULL ACCELERATION. The parties agree that paragraph 1 of the Addendum
to the Option Agreement is hereby deleted in its entirety with respect to the
150,000 Shares Option and replaced by paragraph 1 set forth below, to provide
for full acceleration of the vesting of the 150,000 Shares Option upon a Change
in Control of the Company:

     "1. In the event of a Change in Control of the Company, the 150,000 Shares
     Option (or any replacement grant), to the extent outstanding at the time
     but not otherwise fully exerciseable, shall automatically accelerate such
     that the 150,000 Shares Option shall, immediately prior to the effective
     date of the change in Control, be fully exercisable for all of the Option
     Shares and may be exercised for any or all of such accelerated Option
     Shares as fully-vested shares of Common Stock."

     2.   ENTIRE AGREEMENT. This Amendment constitutes the duly authorized,
valid and binding obligation of each of the parties hereto. Except as
specifically modified by this Amendment, the Option Agreement shall remain in
full force and effect. Any further amendment, change or modification of the
Option Agreement shall be void unless in writing and signed by all parties
hereto.

     3.   COUNTERPARTS. This Amendment may be executed in one or more
counterparts, each of which shall be deemed an original but all of which
together shall constitute one and the same instrument, and all signatures need
not appear on any one counterpart.

<Page>

     IN WITNESS WHEREOF, the parties have duly executed this Amendment as of the
date first above written.

HOOVER'S, INC.                                      OPTIONEE

By:
   -------------------------------
Name:                                               ----------------------------
     -----------------------------                  JEFFREY R. TARR
Title:
      ----------------------------
Date:                                               Date:
     -----------------------------                       -----------------------<Page>

                                                                   EXHIBIT 10.22

                                  AMENDMENT TO
                      HOOVER'S, INC. STOCK OPTION AGREEMENT

     THIS AMENDMENT TO HOOVER'S, INC. STOCK OPTION AGREEMENT (this "AMENDMENT")
is entered into and made effective as of the 13th day of May, 2002 (the
"EFFECTIVE DATE"), by and between Hoover's, Inc., a corporation organized under
the laws of Delaware (the "CORPORATION"), and Jeffrey R. Tarr, who is an
Employee and the Chairman of the Board of Directors of the Corporation
("OPTIONEE"). Capitalized terms not otherwise defined herein shall be as set
forth in the Option Agreement, as defined below.

                                 R E C I T A L S

     WHEREAS, the Corporation entered into a Hoover's, Inc. Stock Option
Agreement dated May 22, 2001 whereby the Corporation granted Optionee an Option
(the "225,000 SHARES OPTION") under The Hoover's, Inc. 1999 Stock Incentive Plan
(the "Plan") to acquire 225,000 shares of Common Stock, $0.01 par value of the
Corporation, at an exercise price of $3.40 per share, such number of shares and
exercise price SUBJECT TO ADJUSTMENT for subsequent stock splits of the
Corporation (the "Option Agreement");

     WHEREAS, the parties desire to amend the Option Agreement to clarify the
definition of a material reduction in Optionee's level of responsibility, for
certain purposes.

     NOW, THEREFORE, in consideration of the foregoing, and the mutual covenants
and conditions herein contained, and for other valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

          1.   The parties agree that paragraph 3(B) of the Addendum to the
Option Agreement is hereby deleted in its entirety with respect to the 225,000
Shares Option and replaced by paragraph 3(B) set forth below:

          "Optionee's voluntary resignation following (A) a change in Optionee's
          position with the Corporation (or Parent or Subsidiary employing
          Optionee) which materially reduces Optionee's level of responsibility,
          with a material reduction in level of responsibility to be considered
          taking in to account all of the facts and circumstances, including
          without limitation the revenues, strategic direction and the number of
          employees of the operation(s) managed by Optionee prior to and
          following such Change in Control; FOR THE AVOIDANCE OF DOUBT, THE
          CHANGE IN OPTIONEE'S STATUS FROM THE CHIEF EXECUTIVE OFFICER OF A
          PUBLIC COMPANY TO THE CHIEF EXECUTIVE OFFICER OF A DIVISION OR A
          SUBSIDIARY OF A PUBLIC OR NON-PUBLIC COMPANY WOULD BE CONSIDERED A
          MATERIAL REDUCTION IN LEVEL OF RESPONSIBILITY FOR THE PURPOSE OF THIS
          PROVISION; (B) any reduction in Optionee's base salary, or a reduction
          in the level of Optionee's other compensation (including fringe
          benefits and target bonus under any performance based bonus or
          incentive programs) by more than fifteen percent (15%) or (C) a
          relocation of Optionee's place of employment by more than thirty (30)
          miles, provided and only if such change, reduction or relocation is
          effected by the Corporation without Optionee's consent."

          2.   ENTIRE AGREEMENT. This Amendment constitutes the duly authorized,
valid and binding obligation of each of the parties hereto. Except as
specifically modified by this Amendment, the Option Agreement shall remain in
full force and effect. Any further amendment, change or modification of the
Option Agreement shall be void unless in writing and signed by all parties
hereto.

<Page>

          3.   COUNTERPARTS. This Amendment may be executed in one or more
counterparts, each of which shall be deemed an original but all of which
together shall constitute one and the same instrument, and all signatures need
not appear on any one counterpart.

          IN WITNESS WHEREOF, the parties have duly executed this Amendment as
of the date first above written.

HOOVER'S, INC.                                      OPTIONEE

By:
   -------------------------------
Name:                                               ----------------------------
     -----------------------------                  JEFFREY R. TARR
Title:
      ----------------------------
Date:                                               Date:
     -----------------------------                       -----------------------<Page>

                                                                   EXHIBIT 10.23

                                 HOOVER'S, INC.
                         NOTICE OF GRANT OF STOCK OPTION

               Notice is hereby given of the following option grant (the
"Option") to purchase shares of the Common Stock of Hoover's, Inc. (the
"Corporation"):

               OPTIONEE: Jeffrey R. Tarr

               GRANT DATE: May 13, 2002

               VESTING COMMENCEMENT DATE: May 13, 2002

               EXERCISE PRICE: $5.30

               NUMBER OF OPTION SHARES: 150,000

               EXPIRATION DATE: May 12, 2012

               TYPE OF OPTION: Options will be deemed Incentive Stock Options to
the extent allowable under the Internal Revenue Code. Remainder will be
considered Non-Qualified Stock Options

               EXERCISE SCHEDULE: The Option shall become exercisable through
November 22, 2006 with periodic vesting as set forth on EXHIBIT A attached
hereto (subject to periodic acceleration triggered by a Change in Control of the
Company as provided in the Stock Option Agreement and Addendum thereto attached
hereto as EXHIBIT B). In no event shall the Option become exercisable for any
additional Option Shares after Optionee's cessation of Service.

               Optionee understands and agrees that the Option is granted
subject to and in accordance with the terms of the Hoover's, Inc. 1999 Stock
Incentive Plan (the "Plan"). Optionee further agrees to be bound by the terms of
the Plan and the terms of the Option as set forth in the Stock Option Agreement
and Addendum thereto attached hereto as EXHIBIT B. A copy of the Plan is
available upon request made to the Corporate Secretary at the Corporation's
principal offices.

               NO EMPLOYMENT OR SERVICE CONTRACT. Nothing in this Notice or in
the attached Stock Option Agreement or in the Plan shall confer upon Optionee
any right to continue in Service for any period of specific duration or
interfere with or otherwise restrict in any way the rights of the Corporation
(or any Parent or Subsidiary employing or retaining Optionee) or of Optionee,
which rights are hereby expressly reserved by each, to terminate Optionee's
Service at any time for any reason, with or without cause.

               DEFINITIONS. All capitalized terms in this Notice shall have the
meaning assigned to them in this Notice or in the attached Stock Option
Agreement.

<Page>

DATED:  May 13, 2002
                                         HOOVER'S, INC.

                                         By:
                                            ------------------------------------
                                         Title: Senior Vice President, CFO

                                         ---------------------------------------
                                         Jeffrey R. Tarr
                                         Address:  8625 Navidad Drive
                                         Austin, Texas 78735

ATTACHMENTS

Exhibit A - Vesting Schedule

Exhibit B - Stock Option Agreement

                                        2
<Page>

                                                                      EXHIBIT A:

     Jeff Tarr Option Grant Vesting Schedule:
     150,000 Option Share Grant @ $5.30 per share, granted on May 13, 2002

<Table>
<Caption>
                                                                            Percentage of
                                                                            Total 150,000
                                                                            shares vested
                                                         Normal             resulting from a
                                    Normal               Vesting            Change of Control
Dates of Vesting                    Vesting %            Shares             on such date
----------------                    ---------            -------            -----------------
<S>                                    <C>               <C>                           <C>
5/13/02  --  8/21/02                     0.00%                 0                       100.00%
8/22/02  --  11/21/02                    2.08%             3,125                       100.00%
11/22/02  --  2/21/03                    4.17%             6,250                       100.00%
2/22/03  --  5/21/03                     6.25%             9,375                        83.30%
5/22/03  --  8/21/03                     8.33%            12,500                       100.00%
8/22/03  --  11/21/03                   12.50%            18.750                        83.30%
11/22/03  --  2/21/04                   16.67%            25,000                        66.70%
2/22/04  --   5/21/04                   20.83%            31,250                        66.70%
5/22/04  --  8/21/04                    25.00%            37,500                       100.00%
8/22/04  --  11/21/04                   31.25%            46,875                       100.00%
11/22/04  --  2/21/05                   37.50%            56,250                       100.00%
2/22/05  --  5/21/05                    43.75%            65,625                       100.00%
5/22/05  --  8/21/05                    50.00%            75,000                       100.00%
8/22/05  --  11/21/05                   58.33%            87,500                       100.00%
11/22/05  --  2/21/06                   66.67%           100,000                       100.00%
2/22/06  --  5/21/06                    75.00%           112,500                       100.00%
5/22/06  --  8/21/06                    83.33%           125,000                       100.00%
8/22/06  --  11/21/06                   91.67%           137,500                       100.00%
11/22/06  --  5/13/12*                 100.00%           150,000                       100.00%
</Table>

*Fully vested through this period.

                                       A-1
<Page>

                                                                       EXHIBIT B

                                 HOOVER'S, INC.
                             STOCK OPTION AGREEMENT

                                    RECITALS

I.        The Board has adopted the Plan for the purpose of retaining the
          services of selected Employees, non-employee members of the Board or
          of the board of directors of any Parent or Subsidiary and consultants
          and other independent advisors who provide services to the Corporation
          (or any Parent or Subsidiary).

II.       Optionee is to render valuable services to the Corporation (or a
          Parent or Subsidiary), and this Agreement is executed pursuant to, and
          is intended to carry out the purposes of, the Plan in connection with
          the Corporation's grant of an option to Optionee.

III.      All capitalized terms in this Agreement shall have the meaning
          assigned to them in the attached Appendix.

               NOW, THEREFORE, it is hereby agreed as follows:

          A.   GRANT OF OPTION. The Corporation hereby grants to Optionee, as of
          the Grant Date, an option to purchase up to the number of Option
          Shares specified in the Grant Notice. The option shares shall be
          purchasable from time to time during the option term specified in
          Paragraph B at the Exercise Price.

          B.   OPTION TERM. This option shall have a maximum term of ten (10)
          years measured from the Grant Date and shall accordingly expire at the
          close of business on the Expiration Date, unless sooner terminated in
          accordance with Paragraph E or F.

          C.   LIMITED TRANSFERABILITY. This option shall be neither
          transferable nor assignable by Optionee other than by will or by the
          laws of descent and distribution following Optionee's death and may be
          exercised, during Optionee's lifetime, only by Optionee. However, if
          this option is designated a Non-Qualfied Option in the Grant Notice,
          then this option may be assigned in whole or in part during Optionee's
          lifetime either as (i) a gift to one or more family members of
          Optionee's Immediate Family, to a trust in which Optionee and/or one
          or more such family members hold more than fifty percent (50%) of the
          beneficial interest or an entity in which more than fifty percent
          (50%) of the voting interests are owned by Optionee and/or one or more
          such family members, or (ii) pursuant to a domestic relations order.
          The assigned portion shall be exercisable only by the person or
          persons who acquire a proprietary interest in the option pursuant to
          such assignment. The terms applicable to the assigned portion shall be
          the same as those in effect for this option immediately prior to such
          assignment and shall be set forth in such documents issued to the
          assignee as the Plan Administrator may deem appropriate.

          D.   DATES OF EXERCISE. This option shall become exercisable for the
          Option Shares in one or more installments as specified in the Grant
          Notice. As the option becomes exercisable for such installments, those
          installments shall accumulate, and the option shall remain exercisable
          for the accumulated installments until the Expiration Date or sooner
          termination of the option term under Paragraph E or F.

                                       B-1
<Page>

          E.   CESSATION OF SERVICE. The option term specified in Paragraph B
          shall terminate (and this option shall cease to be outstanding) prior
          to the Expiration Date should any of the following provisions become
          applicable:

               a.   Should Optionee cease to remain in Service for any reason
                    (other than death, Permanent Disability or Misconduct) while
                    this option is outstanding, then this option shall remain
                    exercisable until the EARLIER of (i) the expiration of the
                    three (3)-month period measured from the date of such
                    cessation of Service or (ii) the Expiration Date.

               b.   Should Optionee die while holding this option, then
                    Optionee's Beneficiary shall have the right to exercise this
                    option until the EARLIER of (A) the expiration of the twelve
                    (12)-month period measured from the date of Optionee's death
                    or (B) the Expiration Date.

               c.   Should Optionee cease Service by reason of Permanent
                    Disability while this option is outstanding, then this
                    option shall remain exercisable until the earlier of (i) the
                    expiration of the twelve (12)-month period measured from the
                    date of such cessation of Service or (ii) the Expiration
                    Date.

               d.   During the applicable post-Service exercise period, this
                    option may not be exercised in the aggregate for more than
                    the number of vested Option Shares for which the option is
                    exercisable on the date of Optionee's cessation of Service.
                    Upon the expiration of the applicable exercise period or (if
                    earlier) upon the Expiration Date, this option shall
                    terminate and cease to be outstanding for any vested Option
                    Shares for which the option has not been exercised. However,
                    this option shall, immediately upon Optionee's cessation of
                    Service for any reason, terminate and cease to be
                    outstanding to the extent this option is not otherwise at
                    that time exercisable for vested shares.

               e.   Should Optionee's Service be terminated for Misconduct or
                    should Optionee engage in Misconduct while this option is
                    outstanding, then this option shall terminate immediately
                    and cease to be outstanding.

          F.   SPECIAL ACCELERATION OF OPTION.

               1. In the event of a Change in Control, this option, to the
extent outstanding at that time but not otherwise fully exercisable, shall
automatically accelerate so that this option shall, immediately prior to the
effective date of the Change in Control, become exercisable for that portion of
the Option Shares as set forth in the Addendum and Attachment hereto at the time
subject to this option and may be exercised for any or all of those Option
Shares as fully-vested shares of Common Stock. In addition, any remaining
unvested shares following such acceleration (the "Remaining Unaccelerated
Shares") shall, immediately prior to the effective date of the Change in
Control, become exercisable for that portion of the Option Shares as set forth
in the Addendum and Attachment hereto at the time subject to this option and may
be exercised for any or all of those Option Shares as fully-vested shares of
Common Stock. No

                                       B-2
<Page>

such acceleration of the Remaining Unaccelerated Shares, however, shall occur if
and to the extent: (i) this option is, in connection with the Change in Control,
assumed or otherwise continued in full force and effect by the successor
corporation (or parent thereof) pursuant to the terms of the Change in Control
or (ii) this option is replaced with a cash incentive program of the successor
corporation which preserves the spread existing at the time of the Change in
Control on the Remaining Unaccelerated Shares (the excess of the Fair Market
Value of those Remaining Unaccelerated Shares over the aggregate Exercise Price
payable for such shares) and provides for subsequent pay-out in accordance with
the same option exercise schedule set forth in the Grant Notice.

               2. Immediately following the consummation of the Change in
Control, this option shall terminate and cease to be outstanding, except to the
extent assumed by the successor corporation (or parent thereof) or otherwise
expressly continued in full force and effect pursuant to the terms of the Change
in Control.

               3. If this option is assumed in connection with a Change in
Control, then this option shall be appropriately adjusted, immediately after
such Change in Control, to apply to the number and class of securities which
would have been issuable to Optionee in consummation of such Change in Control
had the option been exercised immediately prior to such Change in Control, and
appropriate adjustments shall also be made to the Exercise Price, provided the
aggregate Exercise Price shall remain the same.

               4. This Agreement shall not in any way affect the right of the
Corporation to adjust, reclassify, reorganize or otherwise change its capital or
business structure or to merge, consolidate, dissolve, liquidate or sell or
transfer all or any part of its business or assets.

          G.   ADJUSTMENT IN OPTION SHARES. Should any change be made to the
          Common Stock by reason of any stock split, stock dividend,
          recapitalization, combination of shares, exchange of shares or other
          change affecting the outstanding Common Stock as a class without the
          Corporation's receipt of consideration, appropriate adjustments shall
          be made to (i) the total number and/or class of securities subject to
          this option and (ii) the Exercise Price in order to reflect such
          change and thereby preclude a dilution or enlargement of benefits
          hereunder.

          H.   STOCKHOLDER RIGHTS. The holder of this option shall not have any
          stockholder rights with respect to the Option Shares until such person
          shall have exercised the option, paid the Exercise Price and become a
          holder of record of the purchased shares.

          I.   MANNER OF EXERCISING OPTION. In order to exercise this option
          with respect to all or any part of the Option Shares for which this
          option is at the time exercisable, Optionee (or any other person or
          persons exercising the option) must take the following actions:

                    a.   Execute and deliver to the Corporation a Notice of
                         Exercise for the Option Shares for which the option is
                         exercised.

                    b.   Pay the aggregate Exercise Price for the purchased
                         shares in one or more of the following forms:

                                       B-3
<Page>

                         (i)    cash or check made payable to the Corporation;

                         (ii)   a promissory note payable to the Corporation,
                                but only to the extent authorized by the Plan
                                Administrator in accordance with Paragraph M;

                         (iii)  shares of Common Stock held by Optionee (or any
                                other person or persons exercising the option)
                                for the requisite period necessary to avoid a
                                charge to the Corporation's earnings for
                                financial reporting purposes and valued at Fair
                                Market Value on the Exercise Date; or

                         (iv)   through a special sale and remittance procedure
                                pursuant to which Optionee (or any other person
                                or persons exercising the option) shall
                                concurrently provide irrevocable instructions
                                (I) to a Corporation-approved brokerage firm to
                                effect the immediate sale of the purchased
                                shares and remit to the Corporation, out of the
                                sale proceeds available on the settlement date,
                                sufficient funds to cover the aggregate Exercise
                                Price payable for the purchased shares plus all
                                applicable income and employment taxes required
                                to be withheld by the Corporation by reason of
                                such exercise and (II) to the Corporation to
                                deliver the certificates for the purchased
                                shares directly to such brokerage firm in order
                                to complete the sale.

                    Except to the extent the sale and remittance procedure is
               utilized in connection with the option exercise, payment of the
               Exercise Price must accompany the Notice of Exercise delivered to
               the Corporation in connection with the option exercise.

                    c.   Furnish to the Corporation appropriate documentation
                         that the person or persons exercising the option (if
                         other than Optionee) have the right to exercise this
                         option.

                    d.   Make appropriate arrangements with the Corporation (or
                         Parent or Subsidiary employing or retaining Optionee)
                         for the satisfaction of all income and employment tax
                         withholding requirements applicable to the option
                         exercise.

               1.   As soon as practical after the Exercise Date, the
Corporation shall issue to or on behalf of Optionee (or any other person or
persons exercising this option) a certificate for the purchased Option Shares,
with the appropriate legends affixed thereto.

               2.   In no event may this option be exercised for any fractional
shares.

                                       B-4
<Page>

          J.   COMPLIANCE WITH LAWS AND REGULATIONS.

               1.   The exercise of this option and the issuance of the Option
Shares upon such exercise shall be subject to compliance by the Corporation and
Optionee with all applicable requirements of law relating thereto and with all
applicable regulations of any stock exchange (or the Nasdaq National Market, if
applicable) on which the Common Stock may be listed for trading at the time of
such exercise and issuance.

               2.   The inability of the Corporation to obtain approval from any
regulatory body having authority deemed by the Corporation to be necessary to
the lawful issuance and sale of any Common Stock pursuant to this option shall
relieve the Corporation of any liability with respect to the non-issuance or
sale of the Common Stock as to which such approval shall not have been obtained.
The Corporation, however, shall use its best efforts to obtain all such
approvals.

          K.   SUCCESSORS AND ASSIGNS. Except to the extent otherwise provided
          in Paragraphs C and F, the provisions of this Agreement shall inure to
          the benefit of, and be binding upon, the Corporation and its
          successors and assigns and Optionee and Optionee's assigns and
          Beneficiaries.

          L.   NOTICES. Any notice required to be given or delivered to the
          Corporation under the terms of this Agreement shall be in writing and
          addressed to the Corporation at its principal corporate offices. Any
          notice required to be given or delivered to Optionee shall be in
          writing and addressed to Optionee at the address indicated below
          Optionee's signature line on the Grant Notice. All notices shall be
          deemed effective upon personal delivery or upon deposit in the U.S.
          mail, postage prepaid and properly addressed to the party to be
          notified.

          M.   FINANCING. The Plan Administrator may, in its absolute discretion
          and without any obligation to do so, permit Optionee to pay the
          Exercise Price for the purchased Option Shares by delivering a
          full-recourse promissory note payable to the Corporation. The terms of
          any such promissory note (including the interest rate, the
          requirements for collateral and the terms of repayment) shall be
          established by the Plan Administrator in its sole discretion.

          N.   CONSTRUCTION. This Agreement and the option evidenced hereby are
          made and granted pursuant to the Plan and are in all respects limited
          by and subject to the terms of the Plan. All decisions of the Plan
          Administrator with respect to any question or issue arising under the
          Plan or this Agreement shall be conclusive and binding on all persons
          having an interest in this option.

          O.   GOVERNING LAW. The interpretation, performance and enforcement of
          this Agreement shall be governed by the laws of the State of Texas
          without resort to that State's conflict-of-laws rules.

          P.   EXCESS SHARES. If the Option Shares covered by this Agreement
          exceed, as of the Grant Date, the number of shares of Common Stock
          which may without stockholder approval be issued under the Plan, then
          this option shall be void with respect to those

                                       B-5
<Page>

          excess shares, unless stockholder approval of an amendment
          sufficiently increasing the number of shares of Common Stock issuable
          under the Plan is obtained in accordance with the provisions of the
          Plan.

          Q.   ADDITIONAL TERMS APPLICABLE TO AN INCENTIVE OPTION. In the event
          this option is designated an Incentive Option in the Grant Notice, the
          following terms and conditions shall also apply to the grant:

                    a.   This option shall cease to qualify for favorable tax
                         treatment as an Incentive Option if (and to the extent)
                         this option is exercised for one or more Option Shares:
                         (A) more than three (3) months after the date Optionee
                         ceases to be an Employee for any reason other than
                         death or Permanent Disability or (B) more than twelve
                         (12) months after the date Optionee ceases to be an
                         Employee by reason of Permanent Disability.

                    b.   No installment under this option shall qualify for
                         favorable tax treatment as an Incentive Option if (and
                         to the extent) the aggregate Fair Market Value
                         (determined at the Grant Date) of the Common Stock for
                         which such installment first becomes exercisable
                         hereunder would, when added to the aggregate value
                         (determined as of the respective date or dates of
                         grant) of the Common Stock or other securities for
                         which this option or any other Incentive Options
                         granted to Optionee prior to the Grant Date (whether
                         under the Plan or any other option plan of the
                         Corporation or any Parent or Subsidiary) first become
                         exercisable during the same calendar year, exceed One
                         Hundred Thousand Dollars ($100,000) in the aggregate.
                         Should such One Hundred Thousand Dollar ($100,000)
                         limitation be exceeded in any calendar year, this
                         option shall nevertheless become exercisable for the
                         excess shares in such calendar year as a Non-Statutory
                         Option.

                    c.   Should the exercisability of this option be accelerated
                         upon a Change in Control, then this option shall
                         qualify for favorable tax treatment as an Incentive
                         Option only to the extent the aggregate Fair Market
                         Value (determined at the Grant Date) of the Common
                         Stock for which this option first becomes exercisable
                         in the calendar year in which the Change in Control
                         occurs does not, when added to the aggregate value
                         (determined as of the respective date or dates of
                         grant) of the Common Stock or other securities for
                         which this option or one or more other Incentive
                         Options granted to Optionee prior to the Grant Date
                         (whether under the Plan or any other option plan of the
                         Corporation or any Parent or Subsidiary) first become
                         exercisable during the same calendar year, exceed One
                         Hundred Thousand Dollars ($100,000) in the aggregate.
                         Should the applicable One Hundred Thousand Dollar
                         ($100,000) limitation be exceeded in the calendar year
                         of such Change in

                                       B-6
<Page>

                         Control, the option may nevertheless be exercised for
                         the excess shares in such calendar year as a
                         Non-Statutory Option.

                    d.   Should Optionee hold, in addition to this option, one
                         or more other options to purchase Common Stock which
                         become exercisable for the first time in the same
                         calendar year as this option, then the foregoing
                         limitations on the exercisability of such options as
                         Incentive Options shall be applied on the basis of the
                         order in which such options are granted.

          R.   LEAVE OF ABSENCE. The following provisions shall apply upon the
          Optionee's commencement of an authorized leave of absence:

                    a.   The exercise schedule in effect under the Grant Notice
                         shall be frozen as of the first day of the authorized
                         leave, and this option shall not become exercisable for
                         any additional installments of the Option Shares during
                         the period Optionee remains on such leave.

                    b.   Should Optionee resume active Employee status within
                         sixty (60) days after the start date of the authorized
                         leave, Optionee shall, for purposes of the exercise
                         schedule set forth in the Grant Notice, receive Service
                         credit for the entire period of such leave. If Optionee
                         does not resume active Employee status within such
                         sixty (60)-day period, then no Service credit shall be
                         given for the period of such leave.

                    c.   If this option is designated as an Incentive Option in
                         the Grant Notice, then the following additional
                         provision shall apply:

                         (i)    If the leave of absence continues for more than
                                ninety (90) days, then this option shall
                                automatically convert to a Non-Statutory Option
                                at the end of the three (3)-month period
                                measured from the ninety-first (91st) day of
                                such leave, unless Optionee's reemployment
                                rights are guaranteed by statute or by written
                                agreement. Following any such conversion of this
                                option, all subsequent exercises of this option,
                                whether effected before or after Optionee's
                                return to active Employee status, shall result
                                in an immediate taxable event, and the
                                Corporation shall be required to collect from
                                Optionee the income and employment withholding
                                taxes applicable to such exercise.

                    d.   In no event shall this option become exercisable for
                         any additional Option Shares or otherwise remain
                         outstanding if Optionee does not resume Employee status
                         prior to the Expiration Date of the option term.

                                       B-7
<Page>

                                                                       EXHIBIT I

                               NOTICE OF EXERCISE

               I hereby notify Hoover's, Inc. (the "Corporation") that I elect
to purchase _________ shares of the Corporation's Common Stock (the "Purchased
Shares") at the option exercise price of $ per share (the "Exercise Price")
pursuant to that certain option (the "Option") granted to me under the
Corporation's 1999 Stock Incentive Plan on ________. Concurrently with the
delivery of this Exercise Notice to the Corporation, I shall hereby pay to the
Corporation the Exercise Price for the Purchased Shares in accordance with the
provisions of my agreement with the Corporation (or other documents) evidencing
the Option and shall deliver whatever additional documents may be required by
such agreement as a condition for exercise. Alternatively, I may utilize the
special broker-dealer sale and remittance procedure specified in my agreement to
effect payment of the Exercise Price.

                                          Date:
                                                --------------------------------
                                          Optionee Address:
                                                            --------------------

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

Print name in exact manner it is to appear on the stock certificate:
                                                                     -----------

Address to which certificate is to be sent, if different from address above:

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

Social Security Number:
                        ------------------------------

Employee Number:
                 -------------------------------------

                                       I-1
<Page>

                                    APPENDIX

               The following definitions shall be in effect under the Agreement:

                                (a)  AGREEMENT shall mean this Stock Option
                                     Agreement.
                                (b)  BENEFICIARY shall mean, in the event the
                                     Plan Administrator implements a beneficiary
                                     designation procedure, the person
                                     designated by Optionee, pursuant to such
                                     procedure, to succeed to Optionee's rights
                                     under the option evidenced by this
                                     Agreement to the extent the option is held
                                     by Optionee at the time of death. In the
                                     absence of such designation or procedure,
                                     the Beneficiary shall be the personal
                                     representative of the estate of Optionee or
                                     the person or persons to whom the option is
                                     transferred by will or the laws of descent
                                     and distribution.
                                (c)  BOARD shall mean the Corporation's Board of
                                     Directors.
                                (d)  CHANGE IN CONTROL shall mean a change in
                                     ownership or control of the Corporation
                                     effected through any of the following
                                     transactions:
                                     (1)  a merger, consolidation or
                                          reorganization approved by the
                                          Corporation's stockholders, unless
                                          securities representing more than
                                          fifty percent (50%) of the total
                                          combined voting power of the voting
                                          securities of the successor
                                          corporation are immediately thereafter
                                          beneficially owned, directly or
                                          indirectly and in substantially the
                                          same proportion, by the persons who
                                          beneficially owned the Corporation's
                                          outstanding voting securities
                                          immediately prior to such transaction.
                                     (2)  any stockholder-approved transfer or
                                          other disposition of all or
                                          substantially all of the Corporation's
                                          assets, or
                                     (3)  the acquisition, directly or
                                          indirectly by any person or related
                                          group of persons (other than the
                                          Corporation or a person that directly
                                          or indirectly controls, is controlled
                                          by, or is under common control with,
                                          the Corporation), of beneficial
                                          ownership (within the meaning of Rule
                                          13d-3 of the 1934 Act) of securities
                                          possessing more than fifty percent
                                          (50%) of the total combined voting
                                          power of the Corporation's

                                   Appendix-1
<Page>

                                          outstanding securities pursuant to a
                                          tender or exchange offer made directly
                                          to the Corporation's stockholders
                                          which the Board recommends such
                                          stockholders to accept.
                                (e)  CODE shall mean the Internal Revenue Code
                                     of 1986, as amended.
                                (f)  COMMON STOCK shall mean the Corporation's
                                     common stock.
                                (g)  CORPORATION shall mean Hoover's, Inc., a
                                     Delaware corporation.
                                (h)  EMPLOYEE shall mean an individual who is in
                                     the employ of the Corporation (or any
                                     Parent or Subsidiary), subject to the
                                     control and direction of the employer
                                     entity as to both the work to be performed
                                     and the manner and method of performance.
                                (i)  EXERCISE DATE shall mean the date on which
                                     the option shall have been exercised in
                                     accordance with Paragraph 9 of the
                                     Agreement.
                                (j)  EXERCISE PRICE shall mean the exercise
                                     price per share as specified in the Grant
                                     Notice.
                                (k)  EXPIRATION DATE shall mean the date on
                                     which the option expires as specified in
                                     the Grant Notice.
                                (l)  FAIR MARKET VALUE per share of Common Stock
                                     on any relevant date shall be determined in
                                     accordance with the following provisions:
                                     (1)  If the Common Stock is at the time
                                          traded on the Nasdaq National Market,
                                          then the Fair Market Value shall be
                                          the closing selling price per share of
                                          Common Stock on the date in question,
                                          as the price is reported by the
                                          National Association of Securities
                                          Dealers on the Nasdaq National Market
                                          or any successor system. If there is
                                          no closing selling price for the
                                          Common Stock on the date in question,
                                          then the Fair Market Value shall be
                                          the closing selling price on the last
                                          preceding date for which such
                                          quotation exists.
                                     (2)  If the Common Stock is at the time
                                          listed on any Stock Exchange, then the
                                          Fair Market Value shall be the closing
                                          selling price per share of Common
                                          Stock on the date in question on the
                                          Stock Exchange determined by the Plan
                                          Administrator to be the primary market
                                          for the Common Stock, as such price

                                   Appendix-2
<Page>

                                          is officially quoted in the composite
                                          tape of transactions on such exchange.
                                          If there is no closing selling price
                                          for the Common Stock on the date in
                                          question, then the Fair Market Value
                                          shall be the closing selling price on
                                          the last preceding date for which such
                                          quotation exists.
                                (m)  GRANT DATE shall mean the date of grant of
                                     the option as specified in the Grant
                                     Notice.
                                (n)  GRANT NOTICE shall mean the Notice of Grant
                                     of Stock Option accompanying the Agreement,
                                     pursuant to which Optionee has been
                                     informed of the basic terms of the option
                                     evidenced hereby.
                                (o)  IMMEDIATE FAMILY of Optionee shall mean
                                     Optionee's child, stepchild, grandchild,
                                     parent, stepparent, grandparent, spouse,
                                     former spouse, sibling, niece, nephew,
                                     mother-in-law, father-in-law, son-in-law,
                                     daughter-in-law, brother-in-law or
                                     sister-in-law, including adoptive
                                     relationships.
                                (p)  INCENTIVE OPTION shall mean an option which
                                     satisfies the requirements of Code Section
                                     422.
                                (q)  MISCONDUCT shall mean the commission of any
                                     act of fraud, embezzlement or dishonesty by
                                     Optionee, any unauthorized use or
                                     disclosure by Optionee of confidential
                                     information or trade secrets of the
                                     Corporation (or any Parent or Subsidiary),
                                     or any intentional wrongdoing by Optionee,
                                     whether by omission or commission, which
                                     adversely affects the business or affairs
                                     of the Corporation (or any Parent or
                                     Subsidiary) in a material manner. The
                                     foregoing definition shall not limit the
                                     grounds for the dismissal or discharge of
                                     Optionee or any other individual in the
                                     Service of the Corporation (or any Parent
                                     or Subsidiary).
                                (r)  NON-STATUTORY OPTION shall mean an option
                                     not intended to satisfy the requirements of
                                     Code Section 422.
                                (s)  NOTICE OF EXERCISE shall mean the notice of
                                     exercise in the form attached hereto as
                                     Exhibit I.
                                (t)  OPTION SHARES shall mean the number of
                                     shares of Common Stock subject to the
                                     option as specified in the Grant Notice.
                                (u)  OPTIONEE shall mean the person to whom the
                                     option is granted as specified in the Grant
                                     Notice.
                                (v)  PARENT shall mean any corporation (other
                                     than the Corporation) in an unbroken chain
                                     of corporations

                                   Appendix-3
<Page>

                                     ending with the Corporation, provided each
                                     corporation in the unbroken chain (other
                                     than the Corporation) owns, at the time of
                                     the determination, stock possessing fifty
                                     percent (50%) or more of the total combined
                                     voting power of all classes of stock in one
                                     of the other corporations in such chain.
                                (w)  PERMANENT DISABILITY shall mean the
                                     inability of Optionee to engage in any
                                     substantial gainful activity by reason of
                                     any medically determinable physical or
                                     mental impairment which is expected to
                                     result in death or has lasted or can be
                                     expected to last for a continuous period of
                                     twelve (12) months or more.
                                (x)  PLAN shall mean the Corporation's 1999
                                     Stock Incentive Plan.
                                (y)  PLAN ADMINISTRATOR shall mean either the
                                     Board or a committee of the Board acting in
                                     its administrative capacity under the Plan.
                                (z)  SERVICE shall mean Optionee's performance
                                     of services for the Corporation (or any
                                     Parent or Subsidiary) in the capacity of an
                                     Employee, a non-employee member of the
                                     board of directors or a consultant or
                                     independent advisor.
                                (aa) STOCK EXCHANGE shall mean the American
                                     Stock Exchange or the New York Stock
                                     Exchange.
                                (bb) SUBSIDIARY shall mean any corporation
                                     (other than the Corporation) in an unbroken
                                     chain of corporations beginning with the
                                     Corporation, provided each corporation
                                     (other than the last corporation) in the
                                     unbroken chain owns, at the time of the
                                     determination, stock possessing fifty
                                     percent (50%) or more of the total combined
                                     voting power of all classes of stock in one
                                     of the other corporations in such chain.

                                   Appendix-4
<Page>

                                    ADDENDUM
                                       TO
                             STOCK OPTION AGREEMENT

               The following provisions are hereby incorporated into, and are
hereby made a part of, that certain Stock Option Agreement (the "Option
Agreement") by and between Hoover's, Inc. (the "Corporation") and Jeffrey R.
Tarr ("Optionee") evidencing the stock option to acquire 150,000 shares of
Common Stock, $0.01 par value of the Corporation, at an exercise price of $5.30
per share (the "150,000 Shares Option") granted on May 13, 2002 to Optionee
under the terms of the Corporation's 1999 Stock Incentive Plan (the "Plan"), and
such provisions shall be effective immediately. All capitalized terms in this
Addendum, to the extent not otherwise defined herein, shall have the meanings
assigned to them in the Option Agreement.

                             ACCELERATION FOLLOWING
                                CHANGE IN CONTROL

          1.   In the event of a Change in Control of the Company, the 150,000
Shares Option (or any replacement grant), to the extent outstanding at the time
but not otherwise fully exercisable, shall automatically accelerate such that
the 150,000 Shares Option shall, immediately prior to the effective date of the
Change in Control, be exercisable for that portion of the Option Shares as set
forth on Attachment A, depending on the date of such CHANGE IN CONTROL, and may
be exercised for any or all of such accelerated Option Shares as fully-vested
shares of Common Stock.

          2.   The Option as accelerated under Paragraph 1 shall remain so
exercisable as provided in the Option Agreement.

          3.   To the extent the provisions of this Addendum are inconsistent
with the Plan, and/or the Stock Option Agreement (including without limitation
Section 6 thereof), this Addendum shall control for all purposes and any
portions of the Plan and/or the Stock Option Agreement which would otherwise
affect Optionee's ability to exercise options referenced in this Addendum will
not apply or interfere with Optionee's rights under this Addendum. .

                                    Addendum
<Page>

     ATTACHMENT A:

     Jeff Tarr Option Grant Vesting Schedule:
     150,000 Option Share Grant @ $5.30 per share, granted on May 13, 2002

<Table>
<Caption>
                                                                                Percentage of
                                                                                Total 150,000
                                                                                shares vested
                                                         Normal                 resulting from a
                                    Normal               Vesting                Change of Control
Dates of Vesting                    Vesting %            Shares                 on such date
----------------------              ---------            -------                -----------------
<S>                                 <C>                  <C>                    <C>
5/13/02  --  8/21/02                  0.00%                    0                100.00%
8/22/02  --  11/21/02                 2.08%                3,125                100.00%
11/22/02  --  2/21/03                 4.17%                6,250                100.00%
2/22/03  --  5/21/03                  6.25%                9,375                 83.30%
5/22/03  --  8/21/03                  8.33%               12,500                100.00%
8/22/03  --  11/21/03                12.50%               18.750                 83.30%
11/22/03  --  2/21/04                16.67%               25,000                 66.70%
2/22/04  --   5/21/04                20.83%               31,250                 66.70%
5/22/04  --  8/21/04                 25.00%               37,500                100.00%
8/22/04  --  11/21/04                31.25%               46,875                100.00%
11/22/04  --  2/21/05                37.50%               56,250                100.00%
2/22/05  --  5/21/05                 43.75%               65,625                100.00%
5/22/05  --  8/21/05                 50.00%               75,000                100.00%
8/22/05  --  11/21/05                58.33%               87,500                100.00%
11/22/05  --  2/21/06                66.67%              100,000                100.00%
2/22/06  --  5/21/06                 75.00%              112,500                100.00%
5/22/06  --  8/21/06                 83.33%              125,000                100.00%
8/22/06  --  11/21/06                91.67%              137,500                100.00%
11/22/06  --  5/13/12*              100.00%              150,000                100.00%
</Table>

*Fully vested through this period.

                                   Attachment

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