Low levels of serum testosterone may have negative implications on morbidity in HIV-infected men. The purpose of this study was to determine demographic and clinical characteristics that predict low serum testosterone among men attending our HIV clinic. A cross-sectional study of 587 HIV-positive male patients who presented at the Louisiana State University HIV Outpatient (HOP) Clinic between August 1997 and January 1999 was conducted. Demographic and clinical characteristics were collected and analysed. Of the 587 men studied, 119 (20.3%) had a serum testosterone level below 400 ng/dl. Significantly more men with low serum testosterone levels had a presence of opportunistic infection (especially HIV wasting syndrome, oesophageal candidiasis, or dementia), CD4+ cell counts below 200 cells/mm3, or were taking megestrol acetate. Early detection of low serum testosterone will allow for expedient testosterone supplementation therapy, which could improve morbidity and quality of life for HIV-infected men.