We explored mothers' and fathers' differential treatment (PDT) of their adolescent offspring in five domains (privileges, chores, affection, discipline, and temporal involvement) and examined how siblings' personal qualities were associated with PDT. Participants were 188 families with first- and secondborn adolescents. Equal treatment was the modal parental style except for privileges and discipline. Even where equal treatment was normative a substantial proportion of parents reported differential treatment. Further, the similarity of the nature of parents' differential treatment varied by domain. Sex was associated with parents' differential temporal involvement. Sex-typed personal qualities were related to parents' differential discipline. Both sex and sex-typed personal characteristics were linked to differential affection. Privileges and chores were associated with age and birth order.