The authors studied 112 cases of child homicide in New York City in 1968-1969 to identify contributing social and psychiatric factors and to determine the fate of the surviving siblings and the degree of involvement of the city's social agencies with the families. There was a pattern of long-term familial child maltreatment extending to the siblings and continuing after the murders. The victims were usually illegitimate preschoolers; the assailants, usually the mothers or their paramours, had backgrounds of assaultiveness and social deviance and killed in impulsive rage. Reports of sexual abuse of victims or of suicide or psychosis among assailants were rare. The authors present case illustrations and offer guidelines for improved prevention by psychiatrists and social workers.