Few studies have investigated the effects of endoscopic sinus surgery (ESS) on olfaction. In particular, the effect of surgical manipulation of the middle turbinate on olfaction has not been established. Using the University of Pennsylvania Smell Identification Test (UPSIT) and patient questionnaires, the authors performed a prospective study of olfaction in 64 patients undergoing ESS. Thirty-eight patients (59%) underwent partial middle turbinate resection; in the remaining 26 patients (41%), the middle turbinate was preserved. All patients were reevaluated approximately 8 weeks after surgery by endoscopic examination, questionnaire, and the UPSIT. Patients who underwent no resection had a median decrease in UPSIT score of 1.4, and those who underwent resection had a median decrease of 0.5; this difference was not statistically significant. Further, no correlation was found between changes in UPSIT score and follow-up time, sex of the patient, or the patient's subjective assessment of postoperative olfaction. It is concluded that middle turbinate resection has no effect on olfaction.