BACKGROUND: There is a high prevalence of bone demineralization among HIV-infected patients but mechanisms of alteration of bone turnover are still unclear and it is thought to be multifactorial. METHODS: A cross-sectional survey of 492 HIV-infected patients within the Aquitaine cohort estimated the prevalence of osteoporosis/osteopenia and investigated associated factors. Bone mineral density of total body, lumbar spine and femoral neck was measured by dual-energy X-ray absorptiometry. Multivariable analyses of the association with HIV disease status, treatment and anthropometric parameters were stratified according to gender. RESULTS: Median age was 43 years (interquartile range, 38-50); 73% were male; 19.7% patients had reached AIDS, 93.1% were treated with HAART; and 28.5% had lipodystrophy. Based on World Health Organization criteria, osteopenia was diagnosed in 54.6% of men [95% confidence interval (CI), 49.4-59.7) and 51.1% of women (95% CI, 42.6-59.6) and osteoporosis in 33.7% of men (95% CI, 28.8-38.6) and 8.3% of women (95% CI, 3.6-13.9). Using a polytomous logistic regression, older age, homosexual transmission group, low body mass index and low HIV plasma viral load were associated with the diagnosis of bone abnormalities in men, whereas older age and low CD4 lymphocyte count nadir were independently associated with osteoporosis/osteopenia in women. The use of HAART was not related to osteoporosis after adjustment (P = 0.58). CONCLUSIONS: This cohort-based survey showed a high prevalence of osteopenia and osteoporosis of multifactorial origin. Mechanisms and consequences of these bone disorders need to be investigated.