Childhood behavior disorders are related to family stress and maladjustment. Little is known, however, about the adjustment of families with preschool-aged children at risk for subsequent behavior disorders. Moreover, fathers' perceptions of child problem behavior and their reactions to it generally have been neglected. Subjects were mothers and fathers of 52 preschool-aged children assigned to one of three groups: control, moderate externalizing, and high externalizing. Higher child externalizing behavior was associated with greater negative family impact, lowered parenting sense of efficacy, and child-rearing practices that were more authoritarian and less authoritative. Mothers and fathers did not differ in actual perceived level of child behavior problems, although both believed that mothers saw more problems. Child Group x Parent interactions indicated that mothers experienced increased stress and a need for help with moderate as well as high child externalizing behaviors, whereas fathers were not elevated on these measures unless the child's externalizing behaviors were high. Implications of these findings for early family intervention are considered.