Transitional cell carcinomas are tumors with a high tendency of local recurrence. The extent of the primary tumor and histopathologic grade incompletely predict the individual outcome. In several studies, measurement of nuclear DNA content has been found to be of prognostic value in bladder cancer. We performed static DNA cytometry on transitional cell carcinomas of 130 patients. DNA parameters were correlated with stage and grade. There was a good correlation between local tumor extent (T category), grading, and DNA parameters. Ta and T1 tumors had significantly lower levels of 5c exceeding rate and DNA grade of malignancy than muscle invasive carcinoma. Well-differentiated carcinoma (G1) also had lower levels than G2 and G3 tumors. As a result of earlier studies, a DNA-based risk-adapted concept for treatment has been developed for superficial tumors. First preliminary results of a clinical study are given in the present paper.