Fourteen cases of juxtacortical osteogenic sarcoma are presented in an attempt to define the relative malignant behavior of this lesion by correlation with the various histopathological characteristics. At least two distinct behavioral patterns are evident: (1) protracted growth with multiple recurrences and eventual cure resulting after major ablative surgery and (2) rapid growth with local recurrences and metastases leading to death from disease. The most malignant of these tumors either formed sparse new bone and fibrous tissue which cytologically appeared to be malignant, or contained pleomorphic spindle-cell sarcoma, often with a prominent cartilaginous component. Patients with the classic, low-grade type of juxtacortical osteogenic sarcoma had tumors which were composed of well differentiated bone trabeculae and fibrous tissue with small islands of cartilage. This study stresses the importance of thorough histopathological evaluation of this group of osteogenic tumors in order to predict their behavior accurately and aid the surgeons to render adequate therapy.