Sexual sadism has been defined ambiguously in the DSM to include both preoccupation with sadistic sexual fantasies and the acting out of such fantasies (with resultant harm or death to the victims). Ideally, the term should be used only for persons in whom such fantasies are acted out in actual behavior. Almost all such persons will be men. There is an overlap between the psychiatric diagnosis of sexual sadism (as behavior) and the concept of evil as the word is used in everyday parlance. The word evil is evoked generally when one comes to learn of (or witness) violent actions of such a nature as to horrify, shock, and disgust us. Evil corresponds, that is, to an emotional reaction when confronted with acts of a particularly horrifying and repugnant type. Violent sexual crimes involving torture of the victim are particularly likely to elicit this response. A common examplar of sexual sadism is the serial killer who experiences orgasm when murdering his victim. Sadistic sexual fantasies are noted in certain adolescents. In some of these the fantasies serves rehearsal for future sadistic sexual acts, especially in adolescents with callous-unemotional personality (who often emerge in adult life as psychopaths). Whereas therapy would usually fail even if such adolescents were brought to treatment early, there are others who experience sadistic sexual fantasies, but for whom these fantasies are ego-alien and disturbing. Patients of the latter type may be amenable to dynamic psychotherapy.