The Epworth sleepiness scale (ESS) is often used clinically to screen for the manifestations of the behavioral morbidity associated to obstructive sleep apnea (OSA). The purpose of this study was to assess the sensitivity of the ESS in the identification of OSA, as defined by an elevated apnea-hypopnea index. A retrospective chart review of 268 consecutive patients diagnosed with OSA at a multidisciplinary sleep medicine clinic was conducted. The ESS obtained a relatively low sensitivity (66%) in the identification of an apnea-hypopnea index of 5 and above at the suggested cutoff of 10 and increased to 76% at 8. The results of the study showed only fair discriminatory ability of the ESS as a screener for OSA. A score of 8 (instead of 10) is suggested as the cutoff among clinic populations being screened for a sleep disorder.