Of 920 patients with histologically confirmed renal cell carcinoma (RCC) seen at University of Texas M. D. Anderson Hospital over a 10-year period, 44 (4.8%) had the sarcomatoid variant. The authors show that, although sarcomatoid RCC has as common denominators with classic RCC in certain epidemiologic parameters such as age and sex, its biologic behavior is different. It is more malignant, has a higher metastatic rate, ultimate recurrence in localized disease which translates to a shorter survival time. Metastasis at presentation, advanced age (older than 59 years) and female sex were a associate with a worse prognosis. This entity is characterized by a high incidence of bone metastasis at presentation (48%) and by a tendency toward pathologic bone fractures. All of the untreated patients died very soon after diagnosis (median, 3.8 months), whereas all of the patients treated with the various systemic modalities initiated only in the presence of metastatic disease survived significantly longer (median, 13.0 months). Of the eight patients who were treated with doxorubicin HCI chemotherapy regimens two (on CYVADIC) showed complete responses and are the only survivors (50, 65 months). Four patients treated with interferon had the longest median survival (41.0 months). These results suggest that CYVADIC chemotherapy should be combined with interferon in this entity. Since surgery is not curative in early stages of sarcomatoid RCC, adjuvant therapy with those agents should be considered.