This study examined family antisocial characteristics according to whether biological fathers live at home and agree to be study participants. Antisocial symptoms were tabulated for 161 clinic-referred children and their parents. Families with fathers at home had fewer paternal, maternal, and child antisocial symptoms, and scored higher on multiple SES indicators, than did families with departed fathers. Antisocial characteristics were highest, and SES was lowest, when fathers could not be located or recruited. Results suggest that requiring father participation (as in family-trio genetic designs) screens out the more antisocial families. Of clinical interest, antisocial behavior in any family member is more likely if the father is absent and nonparticipating. The heightened antisocial behavior in children associated with absent biological fathers was not mitigated by presence of stepfathers and was not accounted for by lower SES. The ethical use of mother report on absent fathers is discussed.