Threat assessment forms a crucial and basic step which, combined with a vulnerability analysis of the target, can provide the basis for a logical, efficient, and cost-effective design of countermeasures. Rather than focusing on a specific individual or group, this approach focuses on the discrete terrorist incident as the unit of analysis and allows the analyst to examine terrorist behavior itself as expressed by actual acts, rather than statements by observers, reporters, or terrorists about such behavior. The incidents are presented in a spread sheet sorted by a group of keywords and an additional memo file supplementing data that is not given in the spread sheet. 4 figures, 6 references. (Author abstract modified)