The effects of oral vanadyl sulfáte (VOSO4) (0.5 mg/kg/day) on anthropometry, body composition, and Performance were investigated in a 12-week, double-blind, placebo-controlled trial involving weight-training volunteers. Performance was assessed in the treatment (VS) and placebo (P) groups using 1 and 10 repetitions maximum (RM) for the bench press and leg extension. Thirty-one subjects completed the trial, with 2 VS subjects withdrawing because of apparent side effects. There were no significant treatment effects for anthropo-metric parameters and body composition during the trial. Both groups had significant improvements in performance but the only significant effect of treatment was a Treatment × Time interaction in the 1 RM leg extension (p=.002), which could have arisen because the VS group had a lower performance at baseline in this test. It was concluded that oral vanadyl sulfáte was ineffective in changing body composition in weight-training athletes, and any modest performance-enhancing effect requires further investigation.