1. Haemophilic cysts are a rare but serious complication of bleeding ilito the musculo-skeletal system. Five cases are reported.

2. The cysts may arise from bleeding into muscle, under periosteum, or into bone.

3. In early cases conservative treatment by immobilisation and replacement therapy should produce resolution.

4. When alarming increase in size or progressive neurovascular compression occurs, excision of the cyst or amputation should be carried out to prevent the dangerous consequences of rupture, sinus formation or chronic infection.