Malignant mixed mullerian tumors (MMMTs) are the most common sarcomatoid neoplasms of the female genital tract. The clinical, histopathological, immunohistochemical, and differential diagnostic features of MMMTs and other gynecologic mixed tumors are discussed in this article. Current concepts regarding the histogenesis and differentiation of these tumors are discussed, with emphasis on biologic and immunohistological data, and the suggestion is made that MMMTs probably represent "metaplastic" (sarcomatoid) carcinomas rather than true carcinosarcomas. Finally, clinicopathological factors that affect the survival of patients with MMMTs are reviewed.