The interface between tumor and bone that is displayed radiographically is a zone of cellular activity. Its radiographic appearance represents the summation of bone lysis and production. This activity and the radiographic details of the resultant margin are an index of the biologic activity of a lesion. The anatomic site and extent of the lesion can be assessed by radiographs and special imaging techniques. Careful analysis of these patterns, when integrated with clinical data, enhances diagnosis, patient management, and therapy.