BACKGROUND. Radiation therapy is an acceptable treatment choice for many cutaneous malignancies. A potential late sequela of ionizing radiation is the development of secondary neoplasms within the treatment field. Although there are well-known cutaneous syndromes in which the use of ionizing radiation is contraindicated, in other clinical situations, physicians may not fully realize the risks associated with this therapeutic modality. OBJECTIVE. Through a case report presentation, a potential adverse consequence of radiation therapy will be discussed. A subsequent review of the literature should allow clinicians to better understand the potential risks of therapeutic radiation. METHODS. A case report and review of the literature are provided. RESULTS. A healthy black male with an unusual distribution of lower extremity squamous cell carcinomas in situ developed a malignant fibrous histiocytoma after radiation therapy. CONCLUSION. Postradiation sarcomas are uncommon complications of radiation therapy; however, the significant metastatic capabilities of these tumors demand that clinicians be aware of the potential risks of primary radiation therapy in the treatment of cutaneous tumors. © 2005 by the American Society for Dermatologic Surgery, Inc.