An initial dose of celecoxib 200 mg was equivalent to celecoxib 400 mg with regard to the margin previously specified at -0.6 in reducing moderate postoperative pain in endoscopic nasal surgery both in analgesic efficacy and anti-inflammatory property. One hundred and twenty patients were included in this prospective randomized controlled study. Patients treated with celecoxib had lower pain scores than controls, pain scores correlating with local PGE2 level. An initial dose of celecoxib 200 mg was equivalent to 400 mg in reducing moderate pain after endoscopic nasal surgery.