Pre-operative and, in some cases, post-operative urine samples from 29 patients with renal cell or urinary bladder carcinoma were compared to samples from 24 healthy persons and 10 patients with nephrolithiasis and 9 patients with other benign disorders of the efferent urinary tract. The specimens were examined for the presence of MCA, CA 125 and BW 495/36-P expressing epithelial cells. The urine concentrations of the soluble antigens MCA and CA 125 were determined simultaneously in urine samples from 35 patients with renal cell or urinary bladder carcinoma, 10 patients with cystitis and 30 healthy individuals. MCA and BW 495/36-P expressing epithelial cells were significantly increased in all pre-operative urine samples of the tumor patients compared to the group of healthy persons. This increase was also seen with CA 125-positive cells in patients with bladder carcinoma, not however in patients with renal cell carcinoma. BW 495/36-P positive cells were also found in both groups of tumor patients in greater numbers than in the patients with nephrolithiasis or other benign urinary tract disorders. Based on a specificity of 97% when compared to the control urine samples, the cytological determination of the antigens MCA, CA 125 and BW 495/36-P in urinary tract cells of all tumor patients revealed a sensitivity of 48%, 33% and 79% as well as a positive predictive value of 92%, 89% and 95%, respectively. The sensitivity of CA 125 increased to 67% upon isolated analysis of patients with bladder carcinoma. The majority of labelled cells were not identifiable as tumor cells morphologically and appeared as normal transitional epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)