The analysis involves examination of the motivations behind nuclear-related crimes that have already occurred and of those behind analogous nonnuclear crimes (such as terrorist raids, arson, or psychotic bombings) that are in some ways similar to potential, but as yet uncommitted, crimes in the nuclear domain. The report concludes that nuclear defenders should anticipate a surprisingly wide range of threats from an equally wide array of potential adversaries who may be animated by ideological, economic, or personal motivations or by some combination of the three. The adversaries include political terrorists who are likely either to perpetrate actions (such as sabotage of nuclear facilities) intended to appeal to opponents of civilian or military nuclear programs or to use coercive actions such as nuclear weapons theft to gain leverage for their group. Other adversaries include antinuclear extremists who might try to interfere with nuclear facility operations directly or indirectly; professional criminals who might be attracted by the lure of power or monetary gain resulting from nuclear theft; psychotics; and employees who might be prompted to take hostile actions because of job frustrations, ideological disillusionment, or other reasons. A wide-ranging defensive strategy is therefore needed that would provide physical and psychological deterrents to nuclear-related crimes, that would defeat any nuclear-related crime that is attempted at the outset, and that would respond effectively to a nuclear-related incident that is not successfully defeated in its opening stages. Footnotes and a chart of possible nuclear-related crimes are included. (Author abstract modified).