Bone marrow is a source of osteoprogenitor cells that are key elements in the process of bone formation and fracture healing. Eight patients with primary sarcomas treated by extensive en bloc resections and reconstruction using internal fixation who developed delayed unions or nonunions were treated by injection of autogeneic bone marrow into the site of failed healing. Five of the eight patients received chemotherapy, with one patient receiving radiation therapy in addition. Bone formation was noted in seven patients after injection. Union was achieved in five of the patients. These results, obtained in difficult clinical circumstances, are encouraging and suggest that autogeneic bone marrow grafting is a useful technique in the treatment of delayed unions and nonunions and warrant further clinical studies.