A system for staging benign and malignant muskuloskeletal lesions is presented. This system, first devised at the University of Florida in 1977, was based on data assembled from 1968 through 1976. It was field tested by the Musculoskeletal Tumor Society and published in Clinical Orthopaedics and Related Research in 1980. In the ensuing five years, the system has undergone refinement. It has recently been adapted by the American Joint Committee Task Force on Bone Tumors and proposed by them to the International Union Against Cancer (IUCC) for international usage. Based upon histologic grade (G), anatomic site (T), and presence or absence of metastases (M), it describes the progressive stages, irrespective of histogenesis, that assess the progressive degrees of risk to which the patient is subject. This system articulates well with current radiologic techniques of staging and serves as a useful guide in the selection of an appropriate definitive surgical procedure. Its usage permits comparative end result studies on the effect of surgical and nonsurgical methods of management.