This volume, the first of a three volume final report, outlines improvements made to ANCET during the research period covered by this report. ANCET is a rapid-running computer model which calculates casualties from a nuclear attack. The model was developed expressly for sensitivity analyses of civil defense systems and components; its structure and logic have been documented in past Research Triangle Institute research reports for the Office of Civil Defense. The improvements to the ANCET model developed during this research period fall into two major categories: (1) prompt effects and (2) fallout. The prompt effects improvements enable the calculation of casualties for a wide variety of approximations to the areal distributions of population or resources. The fallout improvements provide two fallout component models to the overall ANCET model; these are: (1) the WSEG-10 model and (2) the WSEG-10 model as modified by the National Academy of Sciences. Descriptions and detailed flow diagrams of ANCET subroutines which incorporate these modifications are included in this volume. In addition, this volume gives program listings for all subroutines which have been altered since the original documentation of the ANCET model.