Thirty-one patients with giant cell tumours of bone (BGCT) were treated at our hospital by a conservative approach between 1975 and 1988. 94% of the tumours were grade III (Campanacci) and the follow up was from 2 to 13 years. In the 20 patients who had a modified intralesional excision (curettage) with bone grafting and cement, 5 recurrences occurred. There was one soft tissue recurrence in the 11 patients who had marginal or wide excisions. All recurrences were in grade III lesions. We conclude that grade III BGCT can be treated by modified intralesional excision provided the articular surfaces and part of the metaphysis are intact.