Some Aspects of Fallout of Concern to Civil Defense In October 1971, the Research Directorate of the Office of Civil Defense, now the Defense Civil Preparedness Agency (DCPA), posed questions on eight aspects of fallout of interest to civil defense. They were sent to the Fallout Subcommittee of the Advisory Committee on Civil Defense in the form given in Appendix A. These topics encompass problems of the basic constraints used in fallout prediction, various perturbations on the standard surface-burst problem, the direct detection of heavy fallout without instruments, and the feasibility of extrapolating predictions on an operational basis. The Subcommittee itself and working groups of the Subcommittee have attempted to answer questions on these topics, several of which were rephrased in interaction and by agreement with DCPA representatives. The resuits of these deliberations are the subject matter of this report, Members of Subcommittee Melvin L. Merritt (Chairman) Eric T. Clarke Frank D. Cluff Robert E. Heft Carl F, Miller R. Robert Rapp Lewis V. Spencer Robert C. Tompkins Gilbert J. Ferber Jack C. Greene Jerome L. Heffter John C. Phillips Richard Park (Secretary) tok May 1973