The relationship between contemporary household family structures at fourth-grade and sixth-grade parent- and teacher-rated aggression was examined in an epidemiologically defined population of urban school children. The relationship between family structure and aggression varied by child gender and by parent and teacher ratings in the home and school, respectively. After taking into account family income, urban area, and fourth-grade aggressive behavior, boys in both mother-father and mother-male partner families were significantly less likely than boys in mother-alone families to be rated as aggressive by teachers. No significant relations between family structure and teacher- or parent-rated aggression were found for girls.