The purpose of this study was to psychometrically test the Adolescent Physical Activity Perceived Benefits and Barriers Scales developed for middle-school-age youth. A total of 206 racially diverse 6th, 7th, and 8th graders completed questionnaires at two time points (2 weeks apart). For the 10-item Perceived Benefits Scale and the 9-item Perceived Barriers Scale, test-retest reliability (r = .70; r = .71, respectively) and internal consistency (Cronbach's alpha was .80 and .79, respectively, at time 1) were supported. Principal components analysis with Varimax rotation was employed to assess construct validity. A 2-factor solution emerged for each scale as predicted. The relationship between both scale scores and self-reported physical activity provided additional evidence of validity. Both instruments were found to be reliable and valid for measuring the perceived benefits of and barriers to physical activity in middle school youth.