With the assumption that domain specificity would significantly influence students' motivation, our study was designed to investigate between- and within-domain relations of task value, perceived autonomy and competence, and achievement goal orientations across physical education and mathematics. Urban adolescents (N = 273, ages 12-14 years) completed questionnaires assessing these motivational constructs in both subjects. Based on our confirmatory factor analyses and fit indexes, all motivational constructs demonstrated strong subject specificity. Strengths of associations between physical education and mathematics differed by individual motivational constructs. Within-domain interrelations of these constructs were not consistent across physical education and mathematics. Our findings suggest that domain specificity in physical education plays a significant role in students' motivation. (Contains 4 tables and 1 figure.)