In examining a family crisis centered in a breakdown of relationships, including a homicide, it is meaningless to speak of causality in linear terms (A causes B) as though the trouble resides in one person. The most fruitful approach is to explore the behavior of an individual family member within a context in which another person or persons is present and exchanges information with that individual, each influencing the other. Each family member's behavior and input for family interactions is simultaneously caused by and causative of behavior in another part of the system. This family systems perspective should be used in diagnosing family dysfunctioning: the entire family context must be assessed for clues as to the multiple factors operating between persons and culminating in the homicidal act. The entire family should be involved in therapy, as all family members must recognize their roles in the dysfunction. The family systems perspective is also helpful in designing preventive intervention. Agencies concerned with child and spouse abuse can intervene when there are sufficient warning signs of potential family violence. Intervention must address the entire family system, so that each person may examine and modify his/her behavior to defuse volatile situations and promote mutually satisfying interactions. Twelve references are listed.