Endoscopic surgery has increased in worldwide popularity for surgery of the paranasal sinus. We studied the effect of the surgery on olfactory disturbance of the patients suffering from chronic sinusitis with nasal polyposis. From January 1992 through December 1992, forty-five patients who had olfactory disturbance and were diagnosed as having bilateral chronic sinusitis with nasal polyposis underwent endoscopic evaluations, ostiomeatal unit computed tomography(OMU-CT), and subsequent functional endoscopic sinus surgery(FESS). Among them, thirty patients were followed-up after the surgery. The patients were evaluated pre- and post-operatively regarding olfactory function with T & T olfactometry. There was improvement in olfaction after FESS. It was concluded that FESS may be employed for the relief of olfactory disturbance caused by chronic sinusitis with nasal polyposis.