The present study was designed to examine the predictive validity of the Drive for Muscularity Scale (DMS; McCreary & Sasse, 2000). The drive for muscularity scale (DMS) is comprised of two subscales: a muscularity-oriented body image (MBI) subscale and a muscularity behavior (MB) subscale. The present study tested whether these subscales predicted two behavioral outcomes in the context of a longitudinal design: use of performance enhancing substances (PES) and weightlifting behavior. One hundred and sixty-one male undergraduates completed a questionnaire that assessed the drive for muscularity, PES use and weightlifting behavior at Time 1 and again 6 weeks later. Results indicated that the MB subscale at Time 1 significantly predicted both changes in PES use and weightlifting behavior controlling for past substance use and past weightlifting behavior. The MBI subscale failed to predict either changes in PES use or weightlifting behavior. Implications and directions for future research are discussed.