For a sample of 440 tenth-grade students, measures were collected to assess the self-concept of academic ability and academic achievement. Self-concept of academic ability was measured by Brookover's Self-concept of Academic Ability (General) Scale and academic achievement by the California Achievement Test. Gills had a higher mean score on self-concept of academic ability and on academic achievement than did boys. A significant positive relationship was found between self-concept of academic ability and academic achievement between boys and girls but the magnitude of the relationship between the two variables was stronger among girls than among boys.