Sleepiness in professional drivers is widely accepted to be an important cause of traffic accidents. Despite growing knowledge of the prevalence of sleepiness in automobile and truck drivers, estimates from different countries vary on the extent to which sleepiness is a cause of motor vehicle accidents. We have performed a study assessing the sleep characteristics and symptoms of disordered sleep as well as sleep related traffic accidents in a group of professional drivers by using a self-reported sleep symptom questionnaire. A hundred drivers with a mean age of 36 years filled out the questionnaire. Respondents were asked, whether they had had an accident and whether they felt like the sleepiness was the main reason. According to the answer of this question whether positive or negative, we divided the subjects into two groups: (1) accident group and (2) no accident group. Then, we compared the characteristics of these two. All sample rate of excessive daytime sleepiness and sleep related traffic accidents were 21% (95% confidence interval, CI 13,1 to 28,9) and 17% (95% CI 10,3 to 24,0) respectively. In the accident group (n=17) only two of subjects (12%) complained of witnessed apneas, nocturnal choking, nocturnal sweating and morning headaches. 35,3% of accident group reported five hours or less of average sleep duration per night whereas only 13,3% of no accident group had five hours or less sleep (p<0,05). In conclusion, this is the first study that reports the rate of sleepiness related traffic accidents in a Turkish group of commercial drivers. All sleepiness related accidents cannot be explained by sleep apnea syndrome. And finally, drivers may be able to decrease their risk of accident if they get sleep more than five hours a night.