Objective: The aim of this study was to evaluate the efficacy and feasibility of two school-based RT programs to improve muscular fitness and body composition in adolescents. Methods: The study was conducted in Australia from July 2008 to June 2009. Participants [n = 108, mean age (SD) = 15.0 (0.7) years] were randomized to free weights (n = 37) or elastic tubing (n = 41) RT groups and a control group was recruited (n = 30). Participants in the RT groups completed 2 sets of 10–12 repetitions on 10 exercises for 8 weeks. Waist circumference, body composition (bioelectrical impedance analysis) and muscular strength (bench press and leg press) were assessed at baseline and posttest. Results: Boys (p < 0.001) and girls (p < 0.01) in both RT groups improved their body composition over the study period. Boys in both RT groups significantly improved both upper and lower body strength and their improvements were significantly greater than changes observed in the control group. Girls in the free weights groups achieved larger improvements in lower body strength compared to the control group (p < 0.05). Conclusions: Free weights and elastic tubing RT are feasible and effective strategies for improving aspects of health-related fitness in adolescents.