This study examined the association between typical parental work hours (including nonemployed parents) and children's behavior in two-parent heterosexual families. Child behavior was measured by the Child Behavior Checklist (CBCL) at ages 5, 8, and 10 in the Western Australian Pregnancy Cohort (Raine) Study ("N" = 4,201 child-year observations). Compared to those whose fathers worked fewer hours per week, children whose fathers worked 55 hours or more per week had significantly higher levels of externalizing behavior. This association was not explained by father-child time during the week, poorer family functioning, or overreactive parenting practice. Further, when stratifying the analysis by child gender, this association appeared to exist only in boys. Mothers' work hours were unrelated to children's behavioral problems. The role of parent and child gender in the relationships between parental work hours and children's behavioral problems, together with mediating factors, warrants further investigation. (Contains 3 tables, 1 figure, and 1 note.)