Studies concerning the father's role in his children's development indicate that imprisonment of fathers contains risks for thir children, particularly boys. All families described in this study were lower middle-class whites, and five were Irish Catholic. Data were collected from assessment interviews with mothers and children, therapeutic sessions with some children, social casework, and followup examinations. The imprisoned father was not contacted. In each family, a male child between the ages of 6 and 13 suddenly demonstrated aggressive and/or antisocial behavior within the first 2 months of the father's imprisonment. Males between 11 and 13 were particularly vulnerable. Younger children frequently showed temporary school phobias. In three families, imprisonment soon led to divorce, while the other families remained intact. The divorced families seemed the most disturbed and had a long history of domestic problems. The adolescent sons imitated their fathers' deviant behavior and increasingly engaged in delinquent activities. Boys in the families that remained intact were younger and exhibited aggressive behaviors in school. All improved with intervention from the clinic and the passage of time. Although these families represented a narrow socioeconomic group, other researchers have documented similar problems in larger and more varied populations. In the families studied, problem behavior erupted suddenly, and mothers were unaware of any connection to the father's imprisonment. All children expressed a sense of loss and sadness in interviews conducted shortly after the father's confinement. In several cases, the change in family relationships resulted in particular stress between mother and son. Girls in the families were not interviewed, but other studies have shown that a daughter's psychological adjustment is also affected by a father's imprisonment. The stigma of imprisonment contributed to the children's aggressive and antisocial behavior. Furthermore, some families had difficulty in telling children about prison and even tried to conceal the truth. The father's incareration posed psychological and financial problems for the wives, who seemed isolated and depressed. These families used the mental health clinic for crisis situations, but were unwilling to accept any long-term helping relationship. Although more research on inmates' families is needed, the findings suggest that families with imprisoned fathers could benefit from immediate assistance with marital, financial, and child management problems. Tables and 24 references are included.