Methods to increase production of natural gas from marginal reserves are being investigated. Because of the potentially large reserves present in the eastern Devonian shales, these materials have been selected for the application and evaluation of novel and existing well fracturing and stimulation techniques. The feasibility of enhancing fracture formation and growth in well stimulation by tailored pulse loading, i.e., shaping the borehole imput pressure-time history to produce a specified fracture pattern is discussed in this report. Specifically, SRI's computational fracture model, NAG-FRAG, was used to evaluate the effect of pulse shape and rock properties in controlling dynamic rock fracture. Preliminary calculations were made of the amount and location of damage in a cylindrical configuration, and laboratory-scale springing experiments were performed to determine the NAG-FRAG fracture parameters of the Devonian shale. The results indicate that in general: the amount and location of tensile cracking in a cylindrical geometry are strongly dependent on the shape of the pulse applied to the borehole; in the range of stress investigated the width of the propagated radial stress pulse is determined largely by the geometry and material properties rather than the shape of the borehole pulse; the shape of the fracture density distribution for a given pulse shape is not strongly dependent on the values of the NAG-FRAG fracture parameters; the magnitude of the circumferential stress occurring in any given annulus of material is little affected by the fracture history of inner annuli; additional calculations are needed in which the interdependence of pulse shape and material properties, such as tensile yield strength, are examined for cylindrical flow; a shear-cracking model should be incorporated into NAF-FRAG; and crack closure and reopening generate instabilities in the calculations.