511 bladder wash cytologic findings in 121 patients receiving intravesical chemoprophylaxis with mitomycin C after transurethral resection of stage pTa to stage pT2 bladder carcinoma were retrospectively analyzed. In 42 recurrent tumors, sensitivity of detection by cytology amounted to 67% in GIII tumors, 56% in GII tumors, and 20% in GI tumors. 16% of G0 tumors were cytologically positive. 33% of a total of 30 endoscopically detected recurrent GI-GIII tumors yielded negative results at bladder wash cytology, the findings were suspicious in 27%, while only 40% of all recurrences had a positive bladder wash cytology. Positive cytologic findings combined with normal endoscopic results were obtained in 24 patients. 15 of these (62%) developed recurrences after a mean interval of 15 months (3-60 months) during or after metaphylaxis. When suspicious findings were included, 20 of 30 carcinomas were detected, while 7 of 12 G0 tumors were overgraded. Bladder wash cytology has its merits for early detection of recurrences, since almost two thirds of the patients with positive cytologic findings and negative endoscopy developed a recurrent tumor at a later date. Whether or not positive cytology combined with negative endoscopic results should lead to therapeutic consequences remains to be discussed.