Five patients with primary multicentric giant-cell tumor of bone (eighteen lesions) were followed for four to fourteen and one-half years from the time of the original diagnosis. Only fifteen such cases (fifty-two lesions) have been reported previously. In our series the course of each lesion was similar to that expected of the monostotic tumor. There was a high incidence of lesions in the small bones of the hand (eleven of the eighteen). The histological features were generally typical, but some lesions had a stroma composed mostly of spindle cells. All of the lesions were excised and there was a recurrence in four patients. Of eight lesions treated by curettage with or without autogenous bone-grafting, six recurred. All lesions in the hand that were treated by curettage recurred. There was only one recurrence of the lesions treated by amputation or en bloc resection. Infection occurred in one patient. There were no metastases.