A 265 Ib. (body mass index, 38.1) male elite bodybuilder suffered focal muscle atrophy that developed in his right vastus lateralis muscle within a month following a painful self-administered injection of testosterone. The subject did not lose any sensory or motor function immediately after the injection; however after several days to weeks, muscle atrophy and paresthesia ensued. The subject had an obvious atrophic zone in the right vastus lateralis muscle with approximately 40% loss of strength when compared to the left leg. In our view, the neuropraxia developed from direct neurotoxic effect of androgens or pressure exerted upon the nerve following injection of a bolus of liquid. This report is indicative of the many potential dangers associated with unsupervised androgen use which may include androgens as potential neurotoxins. (C) 1997 Inter Press, Inc.