Osteoporosis in adult males is an under-recognized problem. Patients with haemophilia have several predisposing factors for developing decreased bone mineral density (BMD) including prolonged periods of immobility, reduced weight bearing and co-morbidities associated with bone loss. To establish prevalence and risk factors associated with decreased BMD in patients with haemophilia. Adults with moderate or severe haemophilia A or B underwent dual-energy X-ray absorptiometry (DXA). BMD was correlated to laboratory values, joint mobility measurements and physical activity questionnaires. Thirty patients completed evaluations. The median age was 41.5 years (range 18-61). Median lowest T-score by DXA was -1.7 (range: -5.8 to +0.6), with the femoral neck being the site of the lowest T-scores. Based on World Health Organization criteria, 70% of patients had decreased BMD. Twenty-seven per cent of the participants (n = 8) had osteoporosis and 43% (n = 13) had osteopenia. Variables associated with increased bone loss included lower serum 25-hydroxyvitamin D levels (P = 0.03), lower body mass index (P = 0.047), lower activity scores (P = 0.02), decreased joint range of motion (P = 0.046), HIV (P = 0.03), HCV (P = 0.02), history of inhibitor (P = 0.01) and age (P = 0.03). Adults with haemophilia are at increased risk for developing osteoporosis. A history of HCV and HIV infections, decreased joint range-of-motion, decreased activity levels, history of an inhibitor and low body weight predict bone loss and suggest a population to target for screening. A high prevalence of vitamin D insufficiency was observed. Future studies should investigate interventions, including vitamin D supplementation, to prevent bone loss and fractures for this at-risk population.