EXHIBIT 99.1



February 23, 2011



XTO Energy Inc.

810 Houston Street, Suite 2000

Fort Worth, TX 76102



| |  |     |  |                                            
| |  | --- |  | -------------------------------------------
| |  | Re: |  | Underlying Properties (100%)               
| |  |     |  | Relating to the Cross Timbers Royalty Trust
| |  |     |  | As of December 31, 2010 - SEC Pricing Case 



Gentlemen:



At your request, Miller and Lents, Ltd. (MLL) estimated the proved reserves and future net revenues as of
December 31, 2010, attributable to the XTO Energy Inc. (XTO) interest in certain oil and gas properties prior to inclusion in the Cross Timbers Royalty Trust, i.e., Underlying Properties (100%). This report was prepared for XTOs use for
reserves and financial planning and completed on January 7, 2011. The properties consist of approximately 2,844 leases and 15,188 wells and are located primarily in New Mexico, Oklahoma, and Texas. The evaluated reserves included 100 percent of
the reserves owned by XTO prior to inclusion in the Cross Timbers Royalty Trust, i.e., Underlying Properties (100%)



MLL performed evaluations, which are designated as the SEC Pricing Case, using price and expense premises specified by you and described
in detail on Attachment 1. The aggregate results of MLLs evaluations are as follows:



|                                              |  |                          |         |  |                     |  |          |                 |  |  |                               |  |  |  |           | 
|--------------------------------------------- |  | ------------------------ | ------- |  | ------------------- |  | -------- | --------------- |  |  | ----------------------------- |  |  |  | --------- | 
|                                              |  | Net Reserves             |         |  | Future Net Revenues | 
|Reserves Category                             |  | Oil andCondensate,MBbls. |         |  | Gas,MMcf            |  |          | Undiscounted,M$ |  |  | Discounted at10% per 
Year,M$ | 
|Working Interest Properties                   | 
|Proved Developed Producing                    |  |                          | 1,745.4 |  |                     |  | 714.8    |                 |  |  | 52,589.3                      |  |  |  | 28,309.6  | 
|                                              |  |                          |         |  |                     |  |          |                 |  |  |                               |  |  |  |           | 
|Subtotal                                      |  |                          | 1,745.4 |  |                     |  | 714.8    |                 |  |  | 52,589.3                      |  |  |  | 28,309.6  | 
|                                              |  |                          |         |  |                     |  |          |                 |  |  |                               |  |  |  |           | 
|Royalty Interest Properties                   |  |                          |         |  |                     |  |          |                 |  |  |                               |  |  |  |           | 
|Proved Developed Producing                    |  |                          | 559.0   |  |                     |  | 27,357.6 |                 |  |  | 175,836.5                     |  |  |  | 85,377.3  | 
|                                              |  |                          |         |  |                     |  |          |                 |  |  |                               |  |  |  |           | 
|Subtotal                                      |  |                          | 559.0   |  |                     |  | 27,357.6 |                 |  |  | 175,836.5                     |  |  |  | 85,377.3  | 
|                                              |  |                          |         |  |                     |  |          |                 |  |  |                               |  |  |  |           | 
|Total Working and Royalty Interest Properties |  |                          |         |  |                     |  |          |                 |  |  |                               |  |  |  |           | 
|Proved Developed Producing                    |  |                          | 2,304.3 |  |                     |  | 28,072.4 |                 |  |  | 228,425.8                     |  |  |  | 113,686.9 | 
|                                              |  |                          |         |  |                     |  |          |                 |  |  |                               |  |  |  |           | 
|Total Proved                                  |  |                          | 2,304.3 |  |                     |  | 28,072.4 |                 |  |  | 228,425.8                     |  |  |  | 113,686.9 | 
|                                              |  |                          |         |  |                     |  |          |                 |  |  |                               |  |  |  |           | 



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|XTO Energy Inc. |  | February 23, 2011
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Proved reserves and future net revenues were estimated in accordance with the provisions
contained in Securities and Exchange Commission Regulation S-X, Rule 4-10(a). The Securities and Exchange Commission definition of proved reserves is shown on Attachment 2 (not included). Gas volumes for each property are stated at the pressure and
temperature bases appropriate for the sales contract or state regulatory authority; therefore, some of the aggregated totals may be stated at a mixed pressure base. No provisions for the possible consequences, if any, of product sales imbalances
were included in our projections since MLL received no relevant data. Estimates of future net revenues and discounted future net revenues are not intended and should not be interpreted to represent fair market values for the estimated reserves. In
MLLs projections, future costs of abandoning facilities and wells were assumed to be offset by salvage values. Estimated costs, if any, for restoration of producing properties to satisfy environmental standards are beyond the scope of this
assignment.



Following Attachment 2 is a list of
exhibits (not included) that include annual projections of future production and net revenues for each reserves category, interest type, and state. Also included in the exhibits are one-line summaries showing the proved reserves and future net
revenues for each property in the total royalty trust, in the working interest category, in the royalty interest category, and in each state. Projections of individual property future production and net revenues are included in separate volumes to
this report. These exhibits and volumes should not be relied upon independently of this narrative.



The proved developed producing reserves and production forecasts were estimated by production decline extrapolations, water-oil ratio trends, P/Z declines, or in a few cases, by volumetric calculations.
For some properties with insufficient performance history to establish trends, MLL estimated future production by analogy with other properties with similar characteristics. The past performance trends of many properties were influenced by
production curtailments, workovers, waterfloods, and/or infill drilling. Actual future production may require that MLLs estimated trends be significantly altered. Reserves estimates from volumetric calculations and from analogies are often
less certain than reserves estimates based on well performance obtained over a period during which a substantial portion of the reserves was produced.



The data employed in MLLs estimations of proved reserves and future net income were provided by XTO. The current expenses for each
lease were obtained from operating statements provided by XTO except for certain leases where XTO deducted items considered by XTO to be nonrecurring expenditures. No overhead was included for those properties operated by XTO. For some properties,
such as large waterfloods, XTO assumed a decline in operating costs due to depleting production that was derived by forecasting a decrease in the property well count. None of the data provided to us by XTO, including, but not limited to, graphical
representations and tabulations of past production performance, well tests and pressures, ownership interests, prices, and operating costs, were verified by us as such was not within the scope of MLLs assignment.



MLL considers the assumptions, data, methods and analytical
procedures used in this report appropriate for the purpose hereof, and we have used all such methods and procedures that we consider necessary and appropriate to prepare the estimates of reserves herein.



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|XTO Energy Inc. |  | February 23, 2011
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The evaluations presented in this report, with the exceptions of those parameters
specified by others, reflect MLLs informed judgments and are subject to the inherent uncertainties associated with interpretation of geological, geophysical, and engineering information. These uncertainties include, but are not limited to,
(1) the utilization of analogous or indirect data and (2) the application of professional judgments. Government policies and market conditions different from those employed in this study may cause (1) the total quantity of oil,
natural gas liquids, or gas to be recovered, (2) actual production rates, (3) prices received, or (4) operating and capital costs to vary from those presented in this report. At this time, MLL is not aware of any regulations that
would affect XTOs ability to recover the estimated reserves. Minor precision inconsistencies in subtotals may exist in the report due to truncation or rounding of aggregated values.



Miller and Lents, Ltd. is an independent oil and gas consulting firm. No director, officer, or key employee of
Miller and Lents, Ltd. has any financial ownership in XTO Energy Inc. or any related company. MLLs compensation for the required investigations and preparation of this report is not contingent on the results obtained and reported, and we have
not performed other work that would affect MLLs objectivity. Preparation of this report was supervised by an officer of Miller and Lents, Ltd., who is a licensed Professional Engineer in the State of Texas and professionally qualified with
more than 25 years of relevant experience in the estimation, assessment, and evaluation of oil and gas reserves.



MLLs work papers and data are in our files and available for review upon request. If you have any questions regarding the above, or
if MLL can be of further assistance, please call.



Yours very truly,MILLER AND LENTS, LTD.Texas Registered Engineering Firm No. F-1442By

/S/ JAMES C. PEARSONJames C. Pearson, P. E.Chairman




JCP/slc



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Attachment 1



12/31/10



Cross Timbers Royalty Trust (100%)



SEC PRICING CASE



|A. Oil Price | Average price during the 12-month period prior to 12/31/10 determined as the arithmetical average of the first-day-of-the-month price for each month during the year 2010. The average price was
$73.20 per barrel and was held constant through the life of the property.
|------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



|B. Gas/NGL Price | Average price during the 12-month period prior to 12/31/10 determined as the arithmetical average of the first-day-of-the-month price for each month during the year 2010. The average price was
$5.42 per Mcf and was held constant through the life of the property.
|---------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



|C. Operating Costs | Current expenses held constant through the life of the property. For some properties, expenses included a variable component that was a constant cost per unit of gas production and a fixed
component that was a constant cost per well completion.
|------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



|D. Discount Rate | 10% per year.
|---------------- | -------------