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                                                                     EXHIBIT 3.1

                                AMENDMENT NO. 2

                                       TO

                                      THE

                              AMENDED AND RESTATED

                                     BYLAWS

                                       OF

                            CARRIZO OIL & GAS, INC.

       The following Amendment No. 2 to the Amended and Restated Bylaws, is
adopted by the Board of Directors of Carrizo Oil & Gas, Inc. (the
"Corporation") as of December 15, 1999:

    1. Article IV, Section 9 of the Amended and Restated Bylaws is amended by
replacing the definition of "Change of Control" in its entirety with the
following:

       "Change in Control" means a change in control of the Corporation
occurring after the date of adoption of these Amended and Restated Bylaws of a
nature that would be required to be reported in response to Item 6(e) of
Schedule 14A of Regulation 14A (or in response to any similar item on any
similar schedule or form) promulgated under the Exchange Act, whether or not
the Corporation is then subject to such reporting requirement; provided,
however, that, without limitation, such a Change in Control shall be deemed to
have occurred if at any time after the date of adoption of these Amended and
Restated Bylaws (i) any "person" (as such term is used in Sections 13(d) and
14(d) of the Exchange Act) is or becomes the "beneficial owner" (as defined in
Rule 13d-3 under the Exchange Act), directly or indirectly, of securities of the
Corporation representing 40% or more of the combined voting power of the
Corporation's then outstanding securities without the prior approval of at least
two-thirds of the members of the Board of Directors in office immediately
prior to such person attaining such percentage interest; (ii) the Corporation
is a party to a merger, consolidation, share exchange, sale of assets or other
reorganization, or a proxy contest, as a consequence of which members of the
Board of Directors in office immediately prior to such transaction or event
constitute less than a majority of the Board of Directors thereafter or (iii)
during any 15-month period, individuals who at the beginning of such period
constituted the Board of Directors (including for this purpose any new director
whose election or nomination for election by the Corporation's shareholders was
approved by a vote of at least two-thirds of the directors then still in office
who were directors at the beginning



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of such period) cease for any reason to constitute at least a majority of the
Board of Directors.

     Nothing in the Shareholders Agreement dated December 15, 1999 among S.P.
Johnson IV, Frank A. Wojtek, Paul B. Loyd, Jr., Douglas A.P. Hamilton, Steven
A. Webster, CB Capital Investors, L.P. ("Chase") and certain other investors
(the "Shareholders Agreement") or in the transactions contemplated by the
Securities Purchase Agreement dated December 15, 1999 among Paul B. Loyd, Jr.,
Douglas A.P. Hamilton, Steven A. Webster, Chase and certain other investors, as
it may be amended from time to time (including the addition of any new parties
thereto), shall constitute a "Change of Control" within the definition in this
Section 9. Without limiting the generality of the foregoing, no "Change of
Control" shall result from the attribution of beneficial ownership directly or
indirectly through the Shareholders Agreement such that a shareholder is deemed
to beneficially own 40% or more of the shares of the Company's common stock
then outstanding (a "40% Holder"), unless such shareholder would be deemed to
be a 40% Holder in the absence of the Shareholders Agreement.




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