The use of anabolic steroids to increase muscle mass has become widespread despite FDA warnings against using these potent drugs to enhance performance. The present investigation was undertaken to determine the effects of 6 weeks administration of Dianabol (methylandrostenolone) upon levels of performance, organ weights, heart rate and systolic blood pressure in adult male albino rats. Animals were injected daily (S.Q.) with a placebo (sesame oil), low dose (μmg/kg) or high dose (5mg/kg) of Dianabol and subjected 5 days/week to one of 3 treatments: sedentary housing, high jumping exercise or treadmill running. At sacrifice, internal organs were extracted and weighed to the nearest mg. Adrenal gland, brain and heart weights significantly increased among runners. Heart, kidney and liver weights significantly increased in rats injected with low doses, whereas, only testes weight decreased in rats exposed to high doses of drug. Performance was not affected by either high or low dose users of Dianabol throughout the week regimen.