This volume constitutes the papers and discussions from a symposium on "Societal Risk Assessment: How Safe is Safe Enough?" held at the General Motors Research Laboratories on October 8-9, 1979. This symposium was the twenty-fourth in an annual series sponsored by the Research Laboratories. Initi ated in 1957, these symposia have as their objective the promotion of the interchange ofknowledge among specialists from many allied disciplines in rapidly developing or changing areas ofscience or technology. Attendees characteristically represent the academic, government, and industrial institutions that are noted for their ongoing activities in the particular area of interest. The objective of this symposium was to develop a balanced view of the current status of societal risk assessment's role in the public policy process and then to establish, if possible, future directions of research. Accordingly, the symposium was structured in two dimensions; certainty versus uncertainty and the subjective versus the objective. Furthermore, people representing extremely diverse discip lines concerned with the perception, quantification, and abatement of risks were brought together to provide an environment that stimulated the exchange of ideas and experiences. The keys to this exchange were the invited papers, arranged into four symposium sessions. These papers appear in this volume in the order of their presentation. The discussions that in turn followed from the papers are also included.