Fifty human subjects were studied and evaluated utilizing posterior rhinomanometry techniques. The main purpose of the investigation was to study the physiologic dynamic range of nasal resistance so that the data might serve as a baseline, not only for evaluation and diagnosis of pathologic states but also for the assessment of nasal responses to various physiologic, drug-induced, or pathologic challenges. Analysis was divided into two parts: first, the evaluation of the average resistance and average change in resistance for each patient, and, second, determination of the maximal amount of change to be expected over 15-minute periods in a healthy subject. These studies give the investigator an idea of the magnitude of change that one might expect in normal physiologic situations, based on the 50 subjects that allowed 1,272 observations for justification of the concept of percent change in nasal resistance and not the value of nasal resistance alone. We concluded that the physiologic change in nasal resistance in a normal individual during a 15-minute interval should be less than 53% of the previous observation of nasal resistance. A change greater than 53% suggests a significant change that cannot be attributed to physiologic variability.