This study applied self-determination theory to investigate the effects of students' autonomous motivation and their perceptions of teacher autonomy support on need satisfaction adjustment, learning achievement, and cardiorespiratory fitness over a 4-month personal conditioning unit. Participants were 253 urban adolescents (121 girls and 132 boys, ages = 12-14 years). Based on a series of multiple regression analyses, perceived autonomy support by teachers significantly predicted students' need satisfaction adjustment and led to learning achievement, especially for students who were not autonomously motivated to learn in physical education. In turn, being more autonomous was directly associated with cardiorespiratory fitness enhancement. The findings suggest that shifts in teaching approaches toward providing more support for students' autonomy and active involvement hold promise for enhancing learning. (Contains 4 tables and 1 note.)