PURPOSE: Weight loss is a strong predictor of morbidity and mortality in human immunodeficiency virus (HIV)-infected patients. Men with acquired immunodeficiency syndrome (AIDS) lose body cell mass. Hypogonadism is also common. This study tested the efficacy of a testosterone transscrotal patch (6 mg/day) in improving body cell mass and treating hypogonadism in these patients. SUBJECTS AND METHODS: This multicenter, randomized, double-blinded, placebo-controlled trial was conducted from August 1995 to October 1996 in 133 men, 18 years of age and older, who had AIDS, 5% to 20% weight loss, and either a low morning serum total testosterone level (<400 ng/dL) or a low free testosterone level (<16 pg/mL). Outcomes included weight, body cell mass as measured using bioelectrical impedance analysis, quality of life, and morning measurements of serum testosterone and dihydrotestosterone levels, lymphocyte subsets, and HIV quantification. RESULTS: There were no significant differences in baseline weight, CD4 cell counts, or HIV serum viral quantification between treatment arms. Morning total and free testosterone levels increased in those treated with testosterone, but not with placebo. Following 12 weeks of treatment there were no differences (testosterone - placebo) in mean weight change (-0.3 kg [95% confidence interval (CI): - 1.4 to 0.8]) or body cell mass (-0.2 kg [95% CI: - 1.0 to 0.6]) in the two groups. There were also no changes in quality of life in either group. CONCLUSION: Hypogonadal men with AIDS and weight loss can achieve adequate morning serum sex hormone levels using a transscrotal testosterone patch. However, this system of replacement does not improve weight, body cell mass, or quality of life.