Data were obtained from personal interviews with 152 criminals and noncriminals in Kansas and Connecticut. A standardized, closed, and open-ended interview, requiring approximately 1-2 hours, was administered to all subjects. The interview covered the subject's demographic characteristics, childhood family relationships, childhood behavior patterns, relationship to animals in childhood, adult behavior patterns, and a closed-ended survey on attitudes toward animals and human aggression. A qualitative analysis focused on situations of animal cruelty and family violence among the subjects. Cruelty to animals encompassed the deliberate infliction of pain on a pet animal, wildlife, or livestock. The 152 subjects reported 373 acts of cruelty to animals in childhood. Aggressiveness was defined by behavioral criteria rather than by reason for incarceration. Childhood cruelty toward animals occurred significantly more often among agressive criminals than among nonaggressive criminals or noncriminals. The occurrence of more than 40 cases of extreme animal cruelty facilitated the development of a preliminary classification of nine distinct motivations for animal cruelty. Family violence, particularly paternal abuse and alcoholism, were significantly more common among aggressive criminals with a history of childhood cruelty toward animals. 7 tables and 46 references. (Author abstract modified)