From the DNA histogram of bladder irrigation specimens obtained by flow cytometry, percent proliferative compartment (% PC; supradiploid cell compartment in the total cell population) was calculated. Percent PC was 9. 3 + 5. 9 (mean + SD) in the control group. In the bladder cancer patients, high grade or high stage tumors had the tendency to show higher % PC values. Therefore, it is considered to be possible to predict the grade or the stage of the tumor from the % PC in some cases. Assuming

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... at the normal upper limit of the % PC is 21. 1 (mean + 2SD of % PC in the control group), 36 bladder tumors were detectable in 39 examinations performed in patients with bladder tumor and the false negative rate was 7. 7%. From the above results it is possible to evaluate the presence or absence of tumor cells and this technique could be applied to the automated cytology in patients with bladder tumor. This technique also provided us with an evaluation of the radicality of TUR-Bt, because the % PC returned to the normal range after curative TUR-Bt while it showed a relatively high value after noncurative TUR-Bt. In the follow-up examinations of three cases with bladder tumor, the value of % PC was decreased after the effective treatment and was elevated on the occasion of tumor recurrence. Our results suggest that flow cytometry may be a valuable addition to the routine urologic examination to follow up conservatively treated patients with superficial bladder tumor.