To assess the treatment outcome of endoscopic sinus surgery (ESS), 1,000 patients with chronic sinusitis and nasal polyp treated between November 1991 and January 1995 were included in this study. Among them, 754 patients (64.8%) had previous operations from 1 to 25 times with an average of 3.7. Before ESS, axial and coronal CT scans were obtained (window width: 1,000 HU, window level: +90 HU; section thickness: 2 mm with 12 to 16 sections). Patients with clinical stages from I to IV were 9.9%, 21.0%, 15.0% and 54.1% respectively. Bilateral ESS was performed in 95% patients, septoplasty in 27.6%, middle meatal antrostomy in 78.5%. The clinical cure rate was 84.0%, 557 patients were considered as primary healing, 283 patients delayed healing and 160 patients had persistent inflammation. Complications were noted in 18 patients. Bleeding during ESS varied from 10 to 1,800 ml (average 180 ml). The indications, preoperative evaluation, control of bleeding, prevention of complications and prognosis were discussed in detail. The article indicated that the important factors to increase the cure rate are postoperative follow-up and systematic treatment.