**Abstract:**

Semiclassical methods, long used in most realms of wave physics, have recently experienced a surge of interest in quantum mechanics, especially in the context of highly chaotic systems. In this talk, discussion will center on a demonstration that accurate approximations of long-time quantum wave propagation can be constructed using the appropriate chaotic trajectories of the classical analog. It shows that pessimistic assessments of a breakdown time of (tau)=ln(1/(Dirac h))/(lambda) in the approximation, where (lambda) measures the rate of exponential separation of trajectories, are incorrect. Recent advances will be briefly summarized. [Support from the National Science Foundation under Grant PHY-9421153 is gratefully acknowledged.]

ASA 133rd meeting - Penn State, June 1997