As functional endoscopic sinus surgery becomes popular as a treatment modality in chronic sinusitis, both radiologic examination and nasal endoscopy play important roles in obtaining good postoperative results and preventing serious surgical complications. The authors employed the sinus screening CT scans which is simplified from the PNS CT scans to save time and cost in getting accurate information before the endoscopic sinus surgery is done. With the result of the sinus screening CT scans, we adopted a staging system which enabled us to make decisions more easily for the types of surgical approach by standardization of extention of the diseases. We analyzed the surgical procedures used in 113 patients for whom the sinus screening CT scans were taken and the endoscopic sinus surgeries were performed from May of 1991 to July of 1992. Among these patients, 64 were followed up, and the results of the sinus surgery were analyzed in terms of postoperative nasal endoscopy and subjective symptoms. The results are as follows : 1) Based on our staging system, stage III was most common (31.4%) followed by stage II (26.6%) and stage IV (21.2%). 2) There was a tendency of performing more extensive surgery as the stage by the sinus screening CT scans becames higher. 3) Among the various subjective symptoms after surgery, anosmia showed the least improvement (46.2%). 4) For postoperative nasal endoscopy, the chance of normal epithelization of the mucosa in the ethmoid sinus decreased as the stage becomes higher. It seems to be helpful to employ a staging system in selecting the types of surgical approach and in predicting the surgical results in the treatment of chronic sinusitis. Further revision of the staging system, especially through more refined prospective study, is encouraged for better surgical results.