We report the cytologic features of eight fine-needle aspirations (FNA) and eight exfoliative specimens of collecting duct carcinoma (CDC) obtained from six patients. The four men and two women ranged in age from 27 to 69 years (mean = 45 yr) and all had advanced stage disease at presentation (one stage III, five stage IV). Five of the six patients died of widespread disease, and one is alive and well (mean survival, 28 mo; range, 11–48 mo). The smears of the FNA and exfoliative specimens were scantly to moderately cellular. Tumor cells showed moderate pleomorphism and were arranged primarily in cohesive groups that rarely had a papillary configuration. Nuclei had irregular nuclear contours, coarse chromatin, and one to three nucleoli. In the majority of cases the cytoplasm was finely vacuolated, and occasionally there were large intracytoplasmic vacuoles. Intracytoplasmic mucin was demonstrated in two aspirates. Psammoma bodies were present in four of the seven fluids. In two patients, the cytologic diagnosis was supported by positive immunostaining for high-molecular-weight keratin and Ulex europaeus agglutinin I lectin. Leu M-1 was focally positive in one case and negative in the other. The cytologic features of CDC were readily identified as malignant; however, they were not distinctive and overlapped with those of high-grade renal cell carcinoma with papillury features and transitional cell carcinoma. © 1995 Wiley-Liss, Inc.