Forty-five habitual snorers (mean respiratory disturbance index = 6) and 22 patients with obstructive sleep apnea syndrome (mean respiratory disturbance index = 36) were examined by polysomnography, radiocephalometry, rhinomanometry, nasopharyngeal videoendoscopy, and acoustic rhinometry. In 97% of these patients, hypertrophy of the inferior nasal turbinates was found by acoustic rhinometry, while increased nasal resistance of various degrees was measured in 93% of all patients by active anterior rhinomanometry. Acoustic rhinometry demonstrated that the most resistive segment was located in the anterior parts of the nasal cavity and was built up by two compartments: the region of the isthmus nasi and the region of the head of the inferior turbinate. In our snoring patients, the cross-sectional areas at the head of the inferior turbinate were always smaller than the cross-sectional areas in the isthmus nasi, which in normal controls presented the minimal cross-sectional values of the whole nasal cavity. While rhino-manometry can only measure the amount of nasal resistance, acoustic rhinometry can clearly determine the exact size and location of the different stenoses in the nasal cavity that contribute to the increased nasal resistance.