OBJECTIVE The exact pathophysiology leading to pharyngeal collapse in obstructive sleep apnea syndrome (OSAS) remains incompletely understood. Prior research has shown that normal men have a longer pharyngeal airway than women, and it has been hypothesized that this difference may play a role in the gender-related differences in OSAS. In the current study, we sought to study the potential relationship between the length of the collapsible pharyngeal segment, the upper airway length (UAL), and the severity of OSAS. METHODS The hospital records were searched for all patients who had had polysomnography and also had had a computed tomography of the neck. A total of 24 such patients were identified who participated (15 men and nine women). RESULTS The UAL, the distance between the lower posterior part of the hard palate bone to the upper posterior part of the hyoid bone, was measured for all participants in the midsagittal plane. A correlation coefficient (Pearson r) of 0.406 was found between Respiratory Disturbance Index (RDI) and UAL (p = 0.049). When UAL was normalized to body height, a correlation coefficient (r) of 0.423 was found (p = 0.039). A gender-related difference in UAL was also found. Men with OSAS were found to have longer UAL even when normalized to body height (p = 0.003, unpaired t test) as compared with OSAS women. CONCLUSIONS This study provides potential clinical relevance to prior studies in normal subjects, by demonstrating that men with OSAS have longer UAL than women with OSAS, independent of body size. In addition, the significant correlation between UAL and OSAS severity suggests that UAL may play a role in the pathophysiology of OSAS. These findings are consistent with our predictions from computational modeling studies.