Pedometer-determined physical activity (PA) is inversely related to body composition in middle-aged adults; however, researchers have not established such a relationship in college students. Objective and Participants: In this study, the authors attempted to characterize PA and examine its relationship with body composition in undergraduate college students (N = 88). Methods: The authors measured the BC of 44 women (M age = 21 ± 1 year, M body mass index [BMI] = 23.9 ± 4 kg/m2) and 44 men (M age = 22 ± 1 year, BMI = 26.9 ± 0.9 kg/m2); participants also wore a pedometer for 7 days and completed a PA questionnaire. Results: Men averaged significantly more steps/day (10,027 ± 3,535) than did women (8,610 ± 2,252). For women only, the authors observed significant correlations between steps/day and body composition variables. Men reported engaging in vigorous PA significantly more often than did women. Conclusions: These findings indicate that men engage in PA more often but that PA is related to body composition only in women. In addition, there is better agreement between pedometer-measured and self-reported PA in college-aged men than women. Copyright © 2008 Heldref Publications.