The subjective estimation of nasal breathing, the flow in anterior rhinomanometry, nasal peak flow and the results of acoustic rhinometry have been investigated in 30 patients before and after decongestion of the nasal mucosa. The aim of this study was to compare the different methods in view of their results. The effect of decongestion can be seen in all methods. A regression analysis showed no significant correlation between these methods. We found the best correlation between subjective estimation and the flow in anterior rhinomanometry at 75 Pa on the side of the better flow. The decisive drawback of the acoustic rhinometry is the fitting between nosepiece and nostril. Because of the influence of extranasal factors on the results of the peak flow measurement, anterior rhinomanometry seems to be the most reliable method to assess nasal air flow.