At this present time, we feel that there is no role for DNA flow cytometry (FCM), or indeed DNA studies by any other method, to be used as a screening procedure for patients with no prior history of bladder cancer due to the high false-positive rate found when monitoring exfoliated urothelial cells. On the other hand, for patients who have had a superficial transitional cell carcinoma (TCC), which has a documented 50% recurrence rate, and depending on pathological features, a progression rate from 7 to 45%, DNA FCM provides a sensitive method to predict future disease recurrence. It provides an extremely effective way to predict future progression and further acts as a method to monitor changes in the malignant potential of the patient's disease. For those patients with a past history of superficial TCC who develop abnormal ploidy without any overt tumor, 80% will, within the next four years, suffer a disease recurrence. For the patient who has a Ta TCC and receives intravesical Bacillus Calmette-Guerin (BCG), the development of abnormal ploidy in bladder washing specimens is the single best indicator for future disease recurrence. Similarly, a negative DNA FCM of a bladder washing at six months after intravesical therapy is an excellent predictor of no further occurrence. In patients with superficial TCC, ploidy of the initial and recurrent tumor predicts for future progression. Half of those patients with stage Ta bladder cancer with two successive aneuploid bladder tumors develop muscle invasive disease within one year, while three-fourths develop advanced disease within two years after recurrence of their second aneuploid lesion.(ABSTRACT TRUNCATED AT 250 WORDS)