It has been previously shown that patients with severe haemophilia and not receiving any prophylactic treatment render a high risk of reduced bone mineral density. The purpose of this study was to evaluate bone mineral density (BMD) in patients with haemophilia of different severity types and treatment. The study group consisted of 26 patients with severe haemophilia (aged 33.6 +/- 2.1) and 16 patients with mild haemophilia (aged 40.2 +/- 3.3). The BMD (g cm(-2)) was measured by dual-energy X-ray absorptiometry (DXA). Physical activity was assessed by a self-report questionnaire. Physical activity was scored as duration (h week(-)) and as metabolic physical activity score by weighing the intensity (MET-h week(-1)). Joints were evaluated according to a physical examination score. There was no significant difference in BMD at lumbar spine L1-L4 (mild, 1.214 vs. severe, 1.175; P = 0.329), total hip (1.085 vs. 1.001, P = 0.114), femoral neck (1.036 vs. 0.977, P = 0.265), trochanter (0.896 vs. 0.820, P = 0.131) and whole body (1.215 vs. 1.183, P = 0.325) between those with mild and severe haemophilia. Based on Z-score, both groups had normal BMD (Z score >-1). In patients with severe haemophilia, there was a significant correlation between joint evaluation score and BMD at total hip (P < 0.0001), femoral neck (P = 0.0003) and trochanter (P = 0.003). Physical activity did not correlate to disease severity. We did not observe a correlation between BMD and severity of haemophilia. The results indicate that the use of factor prophylaxis since early childhood may preserve normal BMD in severe haemophilia.