Obstructive sleep apnea (OSA) has a marked male predominance. To determine whether there are differences in the mechanical properties of the pharynx of men and women that may contribute to the gender difference in disease incidence, we measured pharyngeal cross-sectional area during quiet breathing in 77 normal men and 98 normal women using the acoustic pulse technique. Standard pulmonary function tests were also performed. Pharyngeal mechanics were studied in 23 men and 34 women by measuring the change in pharyngeal area during a slow vital capacity maneuver. Gender was found to be the most important independent factor contributing to pharyngeal size. The men had a significantly larger pharynx than the women (3.63 +/- 0.10 versus 3.20 +/- 0.09 cm2, mean +/- SEM; p < 0.01). Pharyngeal mechanics were also different between men and women. The men had a larger change in pharyngeal area with changing lung volume than the women (0.60 +/- 0.14 versus 0.12 +/- 0.12 cm2, mean +/- SEM; p < 0.02). This difference persisted even after normalizing the data for pharyngeal size. We found that there are gender-related differences in the size and mechanical properties of the pharynx and speculate that the larger pharynx of men may be more than offset by greater changes in pharyngeal size with changing lung volume, contributing to the greater incidence of OSA in men.