Younger siblings of adolescents with histories of antisocial behavior are at high risk for developing conduct problems. Information about risk exposure in youths at familial risk for conduct problems is critical to the design of informed preventive interventions. The prevalence of well-validated risk factors for conduct problems was examined in a sample of 92 preschool-aged siblings of adjudicated youths. As expected, preschoolers at familial risk for conduct problems were exposed to a range of sociocultural, biological, and parenting risks. Risk exposure was associated with concurrent conduct problems and social competence in the preschool period. Only a minority of preschoolers was reported by parents to have clinically significant conduct problems, and this subgroup had more risks than children with conduct problems in the normal range. Findings are discussed in the context of preventive interventions for high-risk children and families.