Forced random noise techniques were used to characterize the effective resistance of the nasal passages in normal subjects and subjects who were candidates for surgical correction of nasal obstruction. The slope of the effective resistance curve was characterized by the average resistances over 3 to 5 Hz and 13 to 15 Hz. Subjects with nasal obstruction had effective nasal resistance curves which were more frequency-dependent than those of normal subjects (p less than 0.05). A mathematical model consisting of two series resistance-inertance elements in parallel was used to simulate the nasal passages. With this model we were able to generate effective resistance curves similar to those measured in both normal and obstructed subjects. The forced random noise technique may be a convenient, noninvasive technique for studying the fluid mechanical properties of airflow in the nasal passages and the effects of pharmacological and surgical interventions on nasal resistance.