Acoustic rhinometry and rhinomanometry were used to evaluate the relationship between nasal cross-sectional areas, nasal resistances, and sensations of nasal patency. These parameters were measured before and after topical application of a nasal decongestant in 78 patients suffering from nasal obstruction. As subjects breathed voluntarily through both nasal cavities, no significant correlation was found between sensation of nasal patency and combined nasal minimum cross-sectional areas (r = .11) or of total airflow resistance (r = -.11) either before or after decongestion. However, when subjects were required to breathe through each nasal cavity separately, a significant correlation was found between ipsilateral sensation of nasal patency and both ipsilateral minimum cross-sectional area pre-decongestion (r = -.53, p < .0001) and post-decongestion (r = -.22, p < .01), and airflow resistance pre-decongestion (r = .42, p < .0001) and post-decongestion (r = .25, p < .01). A significant, negative, nonlinear relationship was also found between nasal minimum cross-sectional area and nasal resistance. Furthermore, acoustic rhinometry demonstrated that small intrusions into the lumen of the nose that might be missed by rhinoscopy produce an exponentially greater increase in nasal resistance measurements by rhinomanometry. The findings were most striking in the valve region. It is concluded that each of these objective and complementary measurement techniques provides a more reliable assessment of nasal patency than subjective evaluation by either patient or clinician and can thus provide valuable guidance in management of the symptom of nasal obstruction.