A major component of the Eastern Gas Shales Project being conducted by the Morgantown Energy Technology Center is the development and evaluation of new and refined stimulation techniques which might be suitable for stimulating Devonian shale wells. As part of the EGSP stimulation development program, several dynamic stimulation techniques employing combinations of explosives and/or propellants are being evaluated through a series of mineback experiments at the Nevada Test Site (NTS). As the experiments being conducted at the NTS are being carried out in one of the volcanic tuff formations found at the site, a complete evaluation of the field-test results will require an adequate knowledge of the mechanical properties of the tuff rock. Several of the research firms and agencies participating in the EGSP have or will conduct calculations to simulate certain aspects of the stimulation treatments being evaluated at the NTS. Science Applications, as one of the firms conducting these evaluations, is employing explicit finite difference programs to simulate in both 1-D and 2-D calculations the various stimulation treatments being evaluated. The proper execution of these calculations requires that suitable material properties be available on the NTS tuff. As the existing data base on the mechanical properties of NTS tuff is limited, it has been necessary to carefully review existing data on the tuff and to generate additional data as required. The review, experiments and evaluation which have been conducted have resulted in the following principle conclusions: ? The yield surface defined by triaxial experiments for the G-Tunnel tuff is significantly lower from that defined for other tuff beds at the NTS. ? Direct-pull tensile strength data obtained within this testing program compares favorably with that obtained by Sandia on the same tuff bed. ? The tensile strength of this rock, although quite variable, is moderately low with values on the order of 1.6 MPa being typical.