Anabolic-androgenic steroids (AAS) are used by athletes to enhance performance and physique. Case reports and observations propose that AAS have mood elevating properties and that chronic use leads to addiction. The aim of this study was to evaluate the subjective and physiological effects of single doses of testosterone. In a double-blind fashion, according to a balanced Latin square, 10 paid adult male volunteers received doses of i.m. testosterone (50, 100 and 200 mg), morphine (10 mg) or placebo for five consecutive days. Subjective and physiological responses were measured during each drug condition. Testosterone produced no significant changes in self-reported or observed measures, unlike morphine, which produced statistically significant changes in several measures, including 'feel the drug', 'like the drug' and 'feel high'. There were no adverse effects of administering high doses of testosterone. In conclusion, single doses of testosterone are devoid of the usual pharmacologic effects that are associated with abuse.