Patients with hemophilia suffer from low bone mineral density (BMD) due to several risk factors including arthropathy and resulting immobility. Recent studies have shown variable frequency of low BMD in this group of patients. This study attempts to assess the prevalence of low BMD (osteoporosis and osteopenia) and the associated risk factors in a group of Iranian hemophilia patients. Patients with moderate or severe hemophilia underwent BMD measurement by dual energy X-ray absorptiometry. The results were correlated with other variables including physical activity, calcium intake and demographic data. Forty two patients with the mean age of 31 years (range 18-72) completed the study. The prevalence of osteoporosis in the spine and the left femoral neck was 23.8 and 14.6 %, respectively, and osteopenia in the spine and femoral neck was seen in 45.2 and 31.7 % of the patients, respectively based on the WHO T-score criteria. We found only cigarette smoking to be significantly related to low BMD (P < 0.001). There were two cases of pathologic fracture at femoral neck and forearm (4.8 %). Low BMD is very common in patients with hemophilia. Appropriate assessment of BMD and control of predisposing factors such as prophylactic factor replacement (to prevent hemarthrosis) and cessation of cigarette smoking are warranted.