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                                                                    EXHIBIT 99.1


                                 March 29, 1999



Carrizo Oil & Gas, Inc.
14811 St. Mary's Lane, Suite 148
Houston, Texas  77079

Gentlemen:

         At your request, we have prepared an estimate of the reserves, future
production, and income attributable to certain leasehold and royalty interests
of Carrizo Oil & Gas, Inc. (Carrizo) as of December 31, 1998. The subject
properties are located in the states of Louisiana and Texas. The income data
were estimated using the Securities and Exchange Commission (SEC) guidelines for
future price and cost parameters.

         The estimated reserves and future income amounts presented in this
report are related to hydrocarbon prices. December 1998 hydrocarbon prices were
used in the preparation of this report as required by SEC guidelines; however,
actual future prices may vary significantly from December 1998 prices.
Therefore, volumes of reserves actually recovered and amounts of income actually
received may differ significantly from the estimated quantities presented in
this report. The results of this study are summarized below.

                                 SEC PARAMETERS
                     Estimated Net Reserves and Income Data
                   Certain Leasehold and Royalty Interests of
                             CARRIZO OIL & GAS, INC.
                             As of December 31, 1998
- -------------------------------------------------------------------------------



                                                                               Proved
                                        -------------------------------------------------------------------------------------
                                                        Developed                                               
                                        ------------------------------------------                                Total
                                           Producing              Non-Producing          Undeveloped              Proved
                                        -----------------       ------------------     ----------------       ---------------
                                                                                                           
NET REMAINING RESERVES
  Oil/Condensate - Barrels                    190,518                  84,612                  82,126              357,256
  Plant Products - Barrels                      1,796                       0                       0                1,796
  Gas - MMCF                                    5,260                   3,826                   1,058               10,144
                                                                                      
INCOME DATA                                                                           
  Future Gross Revenue                    $12,502,069             $ 8,431,150             $ 2,921,052          $23,854,271
  Deductions                                3,078,834               2,115,616               1,196,253            6,390,703
                                          -----------             -----------             -----------          -----------
  Future Net Income (FNI)                 $ 9,423,235             $ 6,315,534             $ 1,724,799          $17,463,568
                                                                                      
  Discounted FNI @ 10%                    $ 8,115,439             $ 4,124,412             $   915,791          $13,155,642


         Liquid hydrocarbons are expressed in standard 42 gallon barrels. All
gas volumes are sales gas expressed in millions of cubic feet (MMCF) at the
official temperature and pressure bases of the areas in which the gas reserves
are located.



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Carrizo Oil & Gas, Inc.
March 29, 1999
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         The future gross revenue is after the deduction of production taxes.
The deductions are comprised of the normal direct costs of operating the wells,
ad valorem taxes, recompletion costs, development costs, and certain abandonment
costs net of salvage. The future net income is before the deduction of state and
federal income taxes and general administrative overhead, and has not been
adjusted for outstanding loans that may exist nor does it include any adjustment
for cash on hand or undistributed income. No attempt was made to quantify or
otherwise account for any accumulated gas production imbalances that may exist.
Gas reserves account for approximately 86 percent and liquid hydrocarbon
reserves account for the remaining 14 percent of total future gross revenue from
proved reserves.

RESERVES INCLUDED IN THIS REPORT

         The proved reserves included herein conform to the definition as set
forth in the Securities and Exchange Commission's Regulation S-X Part 210.4-10
(a) as clarified by subsequent Commission Staff Accounting Bulletins. The
definition of proved reserves is included in the section entitled "Definitions
of Reserves" which is attached with this report.

         The proved developed non-producing reserves included herein are
comprised of shut-in and behind pipe categories. The various reserve status
categories are defined in the section entitled "Reserve Status Categories (SEC)"
which is attached with this report.

ESTIMATES OF RESERVES

         In general, the reserves included herein were estimated by performance
methods or the volumetric method; however, other methods were used in certain
cases where characteristics of the data indicated such other methods were more
appropriate in our opinion. The reserves estimated by the performance method
utilized extrapolations of various historical data in those cases where such
data were definitive. Reserves were estimated by the volumetric method in those
cases where there were inadequate historical performance data to establish a
definitive trend or where the use of production performance data as a basis for
the reserve estimates was considered to be inappropriate.

         The reserves included in this report are estimates only and should not
be construed as being exact quantities. They may or may not be actually
recovered, and if recovered, the revenues therefrom and the actual costs related
thereto could be more or less than the estimated amounts. Moreover, estimates of
reserves may increase or decrease as a result of future operations.

FUTURE PRODUCTION RATES

         Initial production rates are based on the current producing rates for
those wells now on production. Test data and other related information were used
to estimate the anticipated initial production rates for those wells or
locations which are not currently producing. If no production decline trend has
been established, future production rates were held constant, or adjusted for
the effects of curtailment where appropriate, until a decline in ability to
produce was anticipated. An estimated rate of decline was then applied to
depletion of the reserves. If a decline trend has been established, this trend
was used as the basis for estimating future production rates. For reserves not
yet on production, sales were estimated to commence at an anticipated date
furnished by Carrizo.

         In general, we estimate that future gas production rates limited by
allowables or marketing conditions will continue to be the same as the average
rate for the latest available 12 months of actual production until such time
that the well or wells are incapable of producing at this rate. The well or
wells were then projected to decline at their decreasing delivery capacity rate.
Our general 





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Carrizo Oil & Gas, Inc.
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policy on estimates of future gas production rates is adjusted when necessary to
reflect actual gas market conditions in specific cases.

         The future production rates from wells now on production may be more or
less than estimated because of changes in market demand or allowables set by
regulatory bodies. Wells or locations which are not currently producing may
start producing earlier or later than anticipated in our estimates of their
future production rates.

HYDROCARBON PRICES

         Carrizo furnished us with prices in effect at December 31, 1998 and
these prices were held constant except for known and determinable escalations.
In accordance with Securities and Exchange Commission guidelines, changes in
liquid and gas prices subsequent to December 31, 1998 were not taken into
account in this report. Future prices used in this report are discussed in more
detail in the section entitled "Hydrocarbon Pricing Parameters" which is
attached with this report.

COSTS

         Operating costs for the leases and wells in this report are based on
the operating expense reports of Carrizo and include only those costs directly
applicable to the leases or wells. When applicable, the operating costs include
a portion of general and administrative costs allocated directly to the leases
and wells under terms of operating agreements. No deduction was made for
indirect costs such as general administration and overhead expenses, loan
repayments, interest expenses, and exploration and development prepayments that
are not charged directly to the leases or wells.

         Development costs were furnished to us by Carrizo and are based on
authorizations for expenditure for the proposed work or actual costs for similar
projects. The estimated net cost of abandonment after salvage was included for
properties where abandonment costs net of salvage are significant. At the
request of Carrizo, their estimate of zero abandonment costs after salvage value
for onshore properties was used in this report. Ryder Scott has not performed a
detailed study of the abandonment costs nor the salvage value and makes no
warranty for Carrizo's estimate.

         Current costs were held constant throughout the life of the properties.

GENERAL


         While it may reasonably be anticipated that the future prices received
for the sale of production and the operating costs and other costs relating to
such production may also increase or decrease from existing levels, such changes
were, in accordance with rules adopted by the SEC, omitted from consideration in
making this evaluation.

         The estimates of reserves presented herein were based upon a detailed
study of the properties in which Carrizo owns an interest; however, we have not
made any field examination of the properties. No consideration was given in this
report to potential environmental liabilities which may exist nor were any costs
included for potential liability to restore and clean up damages, if any, caused
by past operating practices. Carrizo has informed us that they have furnished us
all of the accounts, records, geological and engineering data, and reports and
other data required for this investigation. The ownership interests, prices, and
other factual data furnished by Carrizo were accepted without 




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Carrizo Oil & Gas, Inc.
March 29, 1999
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independent verification. The estimates presented in this report are based on
data available through November 1998.

         Neither we nor any of our employees have any interest in the subject
properties and neither the employment to make this study nor the compensation is
contingent on our estimates of reserves and future income for the subject
properties.

         This report was prepared for the exclusive use and sole benefit of
Carrizo Oil & Gas, Inc. The data, work papers, and maps used in this report are
available for examination by authorized parties in our offices. Please contact
us if we can be of further service.

                                                   Very truly yours,

                                                   RYDER SCOTT COMPANY
                                                   PETROLEUM  ENGINEERS



                                                   Michael F. Stell, P.E.
                                                   Vice President
MFS/sw




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                             DEFINITIONS OF RESERVES



PROVED RESERVES  (SEC DEFINITION)

         Proved reserves of crude oil, condensate, natural gas, and natural gas
liquids are estimated quantities that geological and engineering data
demonstrate with reasonable certainty to be recoverable in the future from known
reservoirs under existing operating conditions, i.e., prices and costs as of the
date the estimate is made. Prices include consideration of changes in existing
prices provided only by contractual arrangements, but not on escalation based on
future conditions.

         Reservoirs are considered proved if economic producibility is supported
by either actual production or conclusive formation test. In certain instances,
proved reserves are assigned on the basis of a combination of core analysis and
electrical and other type logs which indicate the reservoirs are analogous to
reservoirs in the same field which are producing or have demonstrated the
ability to produce on a formation test. The area of a reservoir considered
proved includes (1) that portion delineated by drilling and defined by fluid
contacts, if any, and (2) the adjoining portions not yet drilled that can be
reasonably judged as economically productive on the basis of available
geological and engineering data. In the absence of data on fluid contacts, the
lowest known structural occurrence of hydrocarbons controls the lower proved
limit of the reservoir.

         Reserves that can be produced economically through the application of
improved recovery techniques are included in the proved classification when
these qualifications are met: (1) successful testing by a pilot project or the
operation of an installed program in the reservoir provides support for the
engineering analysis on which the project or program was based, and (2) it is
reasonably certain the project will proceed. Improved recovery includes all
methods for supplementing natural reservoir forces and energy, or otherwise
increasing ultimate recovery from a reservoir, including (1) pressure
maintenance, (2) cycling, and (3) secondary recovery in its original sense.
Improved recovery also includes the enhanced recovery methods of thermal,
chemical flooding, and the use of miscible and immiscible displacement fluids.

         Proved natural gas reserves are comprised of non-associated, associated
and dissolved gas. An appropriate reduction in gas reserves has been made for
the expected removal of natural gas liquids, for lease and plant fuel, and for
the exclusion of non-hydrocarbon gases if they occur in significant quantities
and are removed prior to sale. Estimates of proved reserves do not include crude
oil, natural gas, or natural gas liquids being held in underground or surface
storage.

         Proved reserves are estimates of hydrocarbons to be recovered from a
given date forward. They may be revised as hydrocarbons are produced and
additional data become available.



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                         RESERVE STATUS CATEGORIES (SEC)



         Reserve status categories define the development and producing status
of wells and/or reservoirs.

PROVED DEVELOPED

         Proved developed oil and gas reserves are reserves that can be expected
to be recovered through existing wells with existing equipment and operating
methods. Additional oil and gas expected to be obtained through the application
of fluid injection or other improved recovery techniques for supplementing the
natural forces and mechanisms of primary recovery should be included as "proved
developed reserves" only after testing by a pilot project or after the operation
of an installed program has confirmed through production response that increased
recovery will be achieved.

         Developed reserves may be subcategorized as producing or non-producing
using the SPE/WPC Definitions:

         Producing
         Reserves sub-categorized as producing are expected to be recovered from
         completion intervals which are open and producing at the time of the
         estimate. Improved recovery reserves are considered producing only
         after the improved recovery project is in operation.

         Non-Producing
         Reserves sub-categorized as non-producing include shut-in and behind
         pipe reserves. Shut-in reserves are expected to be recovered from (1)
         completion intervals which are open at the time of the estimate but
         which have not started producing, (2) wells which were shut-in for
         market conditions or pipeline connections, or (3) wells not capable of
         production for mechanical reasons. Behind pipe reserves are expected to
         be recovered from zones in existing wells, which will require
         additional completion work or future recompletion prior to the start of
         production.

PROVED UNDEVELOPED

         Proved undeveloped oil and gas reserves are reserves that are expected
to be recovered from new wells on undrilled acreage, or from existing wells
where a relatively major expenditure is required for recompletion. Reserves on
undrilled acreage shall be limited to those drilling units offsetting productive
units that are reasonably certain of production when drilled. Proved reserves
for other undrilled units can be claimed only where it can be demonstrated with
reasonable certainty that there is continuity of production from the existing
productive formation. Estimates for proved undeveloped reserves are attributable
to any acreage for which an application of fluid injection or other improved
technique is contemplated, only when such techniques have been proved effective
by actual tests in the area and in the same reservoir.




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                         HYDROCARBON PRICING PARAMETERS

                  SECURITIES AND EXCHANGE COMMISSION PARAMETERS



OIL AND CONDENSATE

         Carrizo furnished us with oil and condensate prices in effect at
December 31, 1998 and these prices were held constant to depletion of the
properties. In accordance with Securities and Exchange Commission guidelines,
changes in liquid prices subsequent to December 31, 1998 were not considered in
this report.

PLANT PRODUCTS

         Carrizo furnished us with plant product prices in effect at December
31, 1998 and these prices were held constant to depletion of the properties.

GAS

         Carrizo furnished us with gas prices in effect at December 31, 1998 and
with its forecasts of future gas prices which take into account SEC guidelines,
current spot market prices, contract prices, and fixed and determinable price
escalations where applicable. In accordance with SEC guidelines, the future gas
prices used in this report make no allowances for future gas price increases
which may occur as a result of inflation nor do they make any allowance for
seasonal variations in gas prices which may cause future yearly average gas
prices to be somewhat lower than December 31, 1998 gas prices. For gas sold
under contract, the contract gas price including fixed and determinable
escalations, exclusive of inflation adjustments, was used until the contract
expires and then was adjusted to the current market price for the area and held
at this adjusted price to depletion of the reserves.