A novel method of assessing anterior nasal patency by flexible fiberoptic rhinoscopy was evaluated in two centers by comparison with active anterior rhinomanometry. Rhinoscopy and rhinomanometry were performed 20 times on each of 14 subjects during 14 to 26 minutes. The procedure was videotaped, and nasal airway area was measured from a video monitor. The mean coefficients of variation for rhinoscopy and rhinomanometry were 14% and 19%, respectively. Another investigator examined five subjects by rhinoscopy 30 times in 15 minutes; the mean coefficient of variation was 9%. These means were not significantly different. Rhinoscopy and rhinomanometry were performed at 30-minute intervals for a 6-hour period in 13 subjects. Three investigators independently evaluated results for changes in nasal function characteristic of the nasal cycle. Rhinoscopy detected the nasal cycle in an average of 72% of subjects and rhinomanometry in 49%. Both methods detected the response to topically applied oxymetazoline and methacholine. Results indicate that, whereas the two procedures evaluate different aspects of nasal function, their precision is similar. Rhinoscopy additionally permits evaluation of nasal mucosal changes occurring from disease or treatment.