A 120-item questionnaire was administered to 750 Irish adolescents, aged 12-17. It measured sex differences in the following variables: academic achievement; educational and occupational aspiration; self-assessment of achievement; assertiveness; and stereotypes toward adult roles and three achievement-related traits (striving, competence, and independence). Findings indicated that: (1) girls, as a total sample and by social class, achieved higher grades than boys; (2) grades declined with age for both sexes; (3) educational aspiration reflected occupational choice rather than aspired level of schooling; (4) adolescents perceived similar educational expectations from both parents, but contrary to parents' expectations, many girls aspired to postsecondary education; (5) neither girls nor boys downgraded their achievement; (6) non-assertive behavior was associated with low grades for both sexes and for most females; (7) over 60% of both sexes had stereotyped perceptions of achievement-related traits; and (8) boys were more likely than girls to perceive stereotyped adult sex roles. It was concluded that the achievement and sex role development of Irish youth were similar to their American counterparts. (CP)