These studies indicate that the vast bulk of private weaponry is not owned for self-protection, but for other reasons. Of the weaponry possessed for defense (about 25 percent of the total armament), some is not for self-protection against crime, but for protection against animals. DMI evidence indicates that this may account for as much as 50 percent of the total defensive ownership. In modern society, a 'psychological belief in safety' should not be dismissed as a trivial benefit. In the case of crimes occurring in potentially deterrable circumstances, the evidence suggests at least some modest deterrent effects of private guns. However, most crimes occur in nondeterrable situations. In general, both costs (accidents or risks) and benefits (self-protection) of gun ownership are far too variable across households with varying characteristics to allow a generalization about whether families should or should not keep guns for protection in the home. The data indicate that at least some of the people who own guns for self-defense actually use them for that purpose; the precise percentage is very difficult to determine, as are the ensuing effects on crime and violence in society as a whole. Tabular data and 47 footnotes are provided.