Sons of substance-abusing (SA+) fathers and sons of control (SA-) fathers were compared on measures of parental discipline, temperament, and problem behavior. It was found that discipline was less effective in 10-12-year-old boys of SA+ parents compared with boys of SA+ parents. Children in the SA+ group also scored higher on the constellation of traits comprising a difficult temperament. IntheSA+group only, parental discipline explained a significant, albeit modest, amount of variance on the Child Behavior Checklist summary scores measuring the externalizing and internalizing behavior of the boys. Temperament did not exercise a moderating influence on the association between parental discipline and behavior.