Sarcomatoid renal cell carcinoma is a well-known entity, but sarcomatoid collecting duct carcinoma has not been reported. We recently encountered five cases. The patients were men whose ages ranged from 59 to 82 years (mean age, 68 years). All presented with gross hematuria and three had abdominal fullness. Tumor size ranged from 6 to 9 cm in greatest dimension. The Fuhrman's nuclear grade of the carcinomatous components was 3 in three cases and 4 in two. The sarcomatoid areas were composed of pleomorphic spindle cells forming a malignant fibrous histiocytomatous pattern in four cases and a fibrosarcomatous pattern in one. The immunohistochemical findings in the carcinomatous and sarcomatoid components were identical. Wide-spectrum anti-cytokeratin cocktail, epithelial membrane antigen, and vimentin antibodies demonstrated immunoreactivity, while Leu-M1 did not react in all five cases. Three of the five tumors were positive for Ulex europaeus agglutinin I lectin. One sarcomatoid carcinoma reacted with monoclonal antibody to high molecular weight keratins, and all five tumors reacted with a monoclonal antibody to low molecular weight keratins. Two patients died at 5 months and 13 months after diagnosis, two are alive with metastatic disease at 1 and 14 months, and one is alive with no evidence of disease at 36 months.