In all except 2 out of the 13 specimens with a histological confirmation of cancer, FISH analysis showed aneusomy 9 (sensitivity 84.61%). Among 6 cases with a negative cystoscopy but a positive FISH analysis, 3 recurred within the following 2 months, while 2 no-recurrent patients continued to show positive FISH findings after 6 months. One patient was considered to be false-positive. Four cases with a negative cystoscopy showed disomy 9 and 2 of them recurred.