Twelve patients who had multiple osteosarcomas without intervening visceral lesions differed sharply from those patients whose multifocal osteosarcomas seemed to arise synchronously. It was not possible to determine whether the metachronous sarcomas represented late metastases or new primary tumors. The significant observation was that patients who had a new lesion were potentially curable. Surgical therapy produced two long-term survivors in the group of twelve patients.