Background: Hypovitaminosis D is highly prevalent among HIV-infected patients. Since hypovitaminosis D is a secondary cause of low bone mineral density (BMD), we assessed its prevalence and associated factors in HIV-infected patients with osteopenia/osteoporosis, compared with HIV-infected patients with normal BMD. Materials & methods: Serum 25-hydroxy vitamin D (25[OH]D) concentration were collected from 149 HIV-infected subjects with low BMD and 36 with normal BMD from April to October, 2010. Regression analyses were fitted to predict the probability of hypovitaminosis D in all patients. Results: Of the 149 patients with low BMD (51.8 ± 8 years old, 76.5% men), 83% had vitamin D insufficiency (<30 ng/ml) and 7.4% had severe deficiency (<10 ng/ml). In comparison, insufficiency was present in 75% of subjects from the group with normal BMD (p = 0.60) and no subject was severely deficient (p = 0.13). Among subjects with low BMD, 1.8% of men had low levels of testosterone, 5.4% of patients had high levels of thyroid-stimulating hormone, (all with normal free thyroxine levels) and 14.6% had high levels of parathyroid hormone. Univariate analysis showed significant associations between hypovitaminosis D and the current use of non-nucleosides (β-coefficient: -3.797; standard deviation: 1.538; p = 0.015), whereas protease inhibitors were associated with higher levels of vitamin D (β-coefficient: 4.640; standard deviation: 1.673; p = 0.006). Conclusion: Hypovitaminosis D was highly prevalent in our patients with low BMD but also in those with normal bone dual x-ray energy absorptionmetry scan. 25(OH)D should be periodically monitored, although the benefit of vitamin D and calcium supplements on bone mineralization has not yet been investigated in this population. © 2012 Future Medicine Ltd.