A new modality is necessary to prevent recurrence of superficial bladder cancer after complete transurethral resection (TUR) because of the high recurrence rate even with current prophylaxis protocols. Prostaglandins (PGs) are known to be produced more in transitional cell carcinoma, and etiologically bladder cancer risk is negatively associated with the intake of non-steroidal anti-inflammatory drugs (NSAIDs), which inhibit cyclooxygenase (COX), the rate-limiting enzyme of the PG production. We have shown the chemopreventive effect of piroxicam, an NSAID, on the N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced rat bladder cancer model. To avoid gastrointestinal side effects of regular NSAIDs, we also showed the chemopreventive effect of nimesulide, a selective inhibitor of the second isoform of COX, COX-2, which does not affect COX-l house-keeping activity in gastrointestinal mucosa on the same model. We also observed induction of COX-2 protein in the rat bladder tumor. In this study, we screened COX-2 protein expression in primary superficial bladder cancer tissues, to elucidate if COX-2 selective inhibitors can be a candidate chemopreventive agent for bladder cancer recurrence. Five and 6 samples of superficial bladder cancer cases with and without recurrence after complete TUR were examined by immunohistochemical analysis. We found more COX-2 protein positive samples in the cases with recurrence than in cases without recurrence. Even though the number of cases examined is small, this result supports our hypothesis that COX-2 contributes to superficial bladder cancer recurrence, thus, selective COX-2 inhibitors can be a candidate chemopreventive agent for the recurrence.