An all-Union session on the geophysical and geochemical consequences of nuclear explosions was commissioned by the AGU Public Affairs Committee and will be given at San Francisco Wednesday morning, December 7, 1983. The session is deliberately restricted to aspects within the domain of the American Geophysical Union, and the social, political, and ethical issues will not be treated explicitly. It is inevitable that such issues will be present in the minds of the speakers and audience, but they cannot be evaluated by rigorous scientific methods. The aim of the session is to examine the possible range of geophysical and geochemical consequences of various scenarios involving nuclear explosions. Such scenarios extend from a single nuclear explosion to a major nuclear exchange involving thousands of weapons. A Wednesday afternoon session at the Fall Meeting will examine atmospheric consequences.