The purpose of this investigation was to study the effect of independently controlled confining pressure and pore pressure on the ultimate axial compressive strength of neat cement cylinders. In trying to achieve this purpose the ultimate strength, deformation, and volume change of the material have been studied. The test program consisted of a variation in confining pressure and pore pressure from 0 to 20, 000 psi. For any one test the confining pressure and pore pressure were held constant and the axial load was increased until failure of the specimen occurred. The results indicated that Mohr's Theory by no means begins to explain the complex nature of the failure of the material. An envelope of failure was defined by the circles of stress; however, the failure angles indicated by Mohr's graphical solution did not compare well with those obtained directly from the specimens. An empirical relation of the form: fm= fc + a p 0.81was presented. This relation was found to represent data previously presented as well as the data in this investigation.