In the 24 months after a sleep breathing laboratory opened in a general hospital, 48 patients thought to have a primary sleep breathing disorder were referred for study. Evaluation of breathing during sleep was most useful in those having excessive daytime sleepiness or unexplained polycythemia. The sleep apnea syndrome was documented in 19 of 24 patients with excessive daytime sleepiness. Of 15 patients with unexplained polycythemia, ten were found to have severe hypoxemia during sleep. This experience suggests that facilities for evaluation of sleep breathing disorders should be available in larger medical centers.