This study assesses a possible independent effect of sleep-related breathing disorders on traffic accidents in long-haul commercial truck drivers. The study design included integrated analysis of recordings of sleep-related breathing disorders, self-reported automotive and company-recorded automotive accidents. A cross-sectional population of 90 commercial long-haul truck drivers 20-64 years of age was studied. Main outcome measures included presence or absence, as well as severity, of sleep-disordered breathing and frequency of automotive accidents. Truck drivers identified with sleep-disordered breathing had a two-fold higher accident rate per mile than drivers without sleep-disordered breathing. Accident frequency was not dependent on the severity of the sleep-related breathing disorder. Obese drivers with a body mass > or = 30 kg/m2 also presented a two-fold higher accident rate than nonobese drivers. We conclude that a complaint of excessive daytime sleepiness is related to a significantly higher automotive accident rate in long-haul commercial truck drivers. Sleep-disordered breathing with hypoxemia and obesity are risk factors for automotive accidents.