PURPOSE: Bladder irrigation specimens are effective for sampling the urothelium for detection of recurrent bladder cancer. These specimens can be evaluated by cytology or quantitative techniques. Proliferation and ploidy changes are readily detected using deoxyribonucleic acid (DNA) cytometry. Tumor associated chromosomal aberrations can be assayed using fluorescence in situ hybridization (FISH). The prognostic values of DNA cytometry, and chromosome 9 and 9p21 FISH on exfoliated cells from bladder irrigation specimens from 61 bladder cancer patients were evaluated. MATERIALS AND METHODS: A total of 61 consecutive bladder irrigation specimens were obtained during cystoscopy. DNA cytometry was performed by image analysis. FISH was performed using a centromeric chromosome 9 probe and a cosmid contig (COSp16) probe to the CDKN2A/p16 tumor suppressor region of 9p21. Proportional hazards regression analysis was performed with statistical software to test the predictor variables of initial patient status (presence of tumor), COSp16 fraction (the proportion of COSp16 signals relative to centromeric probe signals), monosomic and hyperdisomic fractions of the chromosome 9 probe, and hyperdiploid fraction from DNA cytometry. Median time to recurrence was calculated using statistical software survival analysis. RESULTS: Initial patient status and monosomy of chromosome 9 were predictive of bladder cancer recurrence (p <0.0001 and p = 0.0073, respectively). The 11 patients with chromosome 9 monosomy fractions greater than 15% and a visible tumor had a median time to recurrence of 105 days. In contrast, only 8 of the 25 patients with chromosome 9 monosomy fractions less than 15% and no visible tumor had recurrence within 560 days. Median time to recurrence was 185 days for 6 patients with chromosome 9 monosomy fractions greater than 15% and no visible tumor, and 225 for 19 with chromosome 9 monosomy fractions less than 15% and a visible tumor. Hyperdiploid fraction was suggestive but not predictive of bladder cancer recurrence (p = 0.078). COSp16 and hyperdisomic fractions were not predictive of bladder tumor recurrence (p = 0.11 and p = 0.30, respectively). CONCLUSIONS: Chromosome 9 monosomy by FISH was predictive of bladder tumor recurrence. Furthermore, our findings support the hypothesis that losses of tumor suppressor genes on chromosome 9 are critical, perhaps initiating genetic events in bladder cancer.