The chemosensitivity of several urological malignancies was determined using a novel dye-exclusion method. The tests proved to be successful in 22 out of 33 urothelial transitional-cell carcinomas, 21 out of 29 renal-cell carcinomas, and in 8 out of 13 testicular tumors, but in 0 out of 4 Wilms' tumors. At 10% of the peak plasma concentration of anticancer drugs achievable after single bolus injection, the sensitivity rates of urothelial transitional-cell carcinomas for cis-platinum, adriamycin, and carboquone were 27.3%, 13.3%, and 5.6%, respectively. At the peak plasma level, urothelial transitional-cell carcinomas were 'susceptible' to cis-platinum, carboquone, and adriamycin, the sensitivity rates being 60%, 50%, and 30%, respectively. The number of these carcinomas susceptible at the peak plasma level was significantly larger than that at 10% of the peak plasma level (P less than 0.01). However, renal-cell carcinomas exhibited a low sensitivity rate of 38% even when exposed to the peak plasma level. A similar trend was observed when tumor chemosensitivity was determined using a modified human tumor clonogenic assay. These results suggest that urothelial transitional-cell carcinomas may show good responses when anticancer drugs are given at high concentrations using methods such as intra-arterial infusion and intravesical instillation.