The almost bewildering variety of lesions that can affect bone contrasts sharply with the limited potential of bone to differentially respond to those lesions. This paradox can create a challenging problem when a bone lesion is shown on an x-ray film. Although heavily populated with pleuripotential primitive mesenchymal cells, there is seldom a histologic or radiographic change in the involved bone specific enough to allow a comfortable diagnostic autonomy to be enjoyed by surgical pathologists, radiologists or orthopaedic surgeons. Even when diligent and astute clinical evaluation has excluded infectious, parasitic, metabolic and metastatic causes of the change seen on x-ray studies, a physician is often still uncertain as to the exact nature of the lesion. A knowledge of the relative frequency of the common lesions, an acceptance that biopsy studies and treatment must be combined at times, an appreciation of the possibility of malignant change in a given lesion and a tendency to seek early consultation will likely lead to timely and accurate diagnosis. Once the diagnosis is made, optimum management must be selected. The best current opinion categorizes the lesions into treatment groups consisting of observation, curettage and graft, block excision, cryotherapy and radiotherapy.