Clinicopathologic studies of 16 homologous and 19 heterologous malignant mesodermal (Mullerian) mixed tumors of the corpora uteri showed that homologous tumors were more common in black women than in white women; in the former, tumors were diagnosed at a younger age and in more advanced stages than in the latter. Fifty-five percent of women with clinical stage I disease had a higher surgicopathologic stage. The most significant prognostic factors were pathologic extent of disease and vascular invasion in the myometrium. There was no difference in outcome between homologous and heterologous tumors. Initial surgery for staging is essential for the adequate evaluation and treatment of these patients.