To evaluate the relationship between change in DNA ploidy and tumor recurrence, 102 patients with superficial bladder carcinoma between January 1989 and December 1993 were studied. 1. Among the 102 patients, 36 patients had 54 cases of recurrence. 2. Overall recurrence rate was 0.0168/month, 0.0172/month in intial diploid group and 0.0163/month in aneuploid. 3. The patients with persistence of a diploid pattern or a change of aneuploid pattern into diploid pattern had lower recurrence rate (36.2%) than patients with persistence of an aneuploid or a change of diploid into aneuploid (53.2%). In conclusion, these results suggest that intial DNA plodiy is not associated with a tumor recurrence, and a change in DNA ploidy seems to have a better prognostic information.