To determine whether HIV infection, the wasting syndrome, or nucleoside analog reverse transcriptase inhibitor (NRTI) or protease inhibitor (PI) therapy uniquely affect fat distribution in men, we performed manual regional analysis of total, appendicular, trunk, and central abdominal fat measured by dual-energy X-ray absorptiometry (DEXA). Five groups of study subjects were identified for this cross-sectional analysis: HIV-negative controls (HIV-; N = 44) and four groups of HIV-positive subjects: antiretroviral (ARV)-naive or with limited prior use of NRTIs (ARV-; N = 23); on NRTIs for > or =6 months but PI-naive (NRTI; N = 30); on an NRTI/PI regimen for > or =6 months but with no complaints of abnormal fat distribution (NRTI/PI; N = 26); and those on NRTIs but PI-naive with the wasting syndrome (NRTI/WS; N = 40). Total, appendicular, trunk, and central abdominal fat was significantly lower in NRTI/WS. The ratio of trunk fat to appendicular fat was virtually identical in HIV- and ARV-. This ratio was significantly higher in the NRTI, NRTI/PI, and NRTI/WS groups, and values in these three groups were similar. These cross-sectional data suggest that HIV-infected men receiving NRTIs have an altered pattern of fat distribution, compared with HIV-negative men and HIV-positive men who are not receiving antiretroviral therapy. This effect was independent of the concomitant use of a PI or a diagnosis of the wasting syndrome. We saw no evidence of a unique effect of HIV infection per se on regional fat distribution. Although the fat ratio is increasingly employed, its physiologic significance is unclear. Our results, which have been obtained retrospectively, are intended to provide the impetus for prospective, controlled studies of the interactions among drug and host factors in the development of fat distribution abnormalities.