OBJECTIVE: This study sought to evaluate the existence and implications of familial aggregation of emotional and behavioral problems of childhood in a general population sample. METHOD: The children included in the study were chosen with the use of a sampling technique that identified households in which there were two or more children aged 4- 16 years living at home at the time of the survey. Ratings on checklists of emotional and behavioral problems were obtained from parents, teachers of children in elementary school, and the children themselves if they were adolescents aged 12-16. Children were classified as having problems if their scores on scales of conduct, attention deficit, or emotional problems were in the top 10% of the distribution of scores from any informant. RESULTS: There was evidence for familial aggregation of these problems, particularly conduct and emotional problems. However, this was largely derived from the parents' reports of symptoms, not the teachers' or adolescents' reports. The degree of familial aggregation varied according to certain sibship characteristics and patterns of comorbidity. CONCLUSIONS: Familial aggregation of emotional and behavioral problems does exist in a community population and is not simply an artifact of clinic attendance.