Some basic properties or plastic flow of the new endochronic plasticity theory are established, using analytical and numerical methods. Particular attention is given to the case, of significant practical importance, in which the theory exhibits a failure surface. The plastic flow properties so established are compared with those of conventional plasticity theory ; it is shown that the two theories, in general, exhibit substantially different plastic flow rules. Also, proofs are given which show that the new endochronic theory satisfies the Postulate of Isotropy and Drucker’s Postulate of Stability in the Small.