AbstractDuring the last decade, there has been a considerable activity in the development of probabilistic model1ing and eva1uating techniques for power system re1iabi1ity eva1uation.During the same period, a continuous deve10pment of better techniques for assessing transient stabi1ity in power systems has been reported but the bulk of this work is based on deterministic mode1s. Very litt1e has been pub1ished on the probabi1istic nature of the basic functions which affect the transient stabi1ity performance of power systems. Scope ofthis paper is to describe the developed computational methods for eva1uating the probabi1ity indices of transient stabi1ity for the Hel1enic Transmission Power System.