To address the high prevalence of diabetes in American Indians (AI) youth we conducted a trial designed to promote exercise behavior in AI adolescents. As part of that trial participants completed questionnaires to assess their attitudes and perceptions about physical activity. The purpose of this analysis was to measure the strength of correlations between those perceptions and body composition, physical activity, and aerobic fitness. METHODS: We enrolled 81 overweight/obese (OW/Ob), non-diabetic AI boys and girls from rural SE Oklahoma, 11-20 years old, with low physical activity, for the exercise intervention, and 39 normal weight (NW) peers from the same communities. A 15-item questionnaire with a 5-point scale was used to record the perceived comfort and enjoyment of physical activity. Body composition was measured with bioelectric impedance, aerobic fitness as peak oxygen uptake (VO2pk) on a cycle ergometer, and physical activity (daily steps) with a pedometer. The OW/Ob group was instructed to exercise 3 days per week for 48 weeks at their local Choctaw Nation wellness center. DISCUSSION: Perception of physical activity among AI adolescents varies with body weight and objectively measured physical activity and aerobic fitness. The same perceptions, however, did not appear to influence the level of participation in the exercise program. Thus, physical activity programs may need to be tailored to address additional barriers to optimize participation.Describe the concept of “perception of activity” and how it can be measured.Measure perception of activity, and factors associated with those perceptions, in AI youth.Determine how information about exercise perceptions may be used to promote physical activity behavior in AI youth.