Three patients with untreated sleep apnea fell asleep while driving and caused serious automobile accidents. One person died, another became permanently paraplegic, and the three patients with sleep apnea were seriously injured in these crashes. This sequela of sleep apnea is not surprising, since subjects with sleep apnea may be poor drivers with a high accident rate and a high incidence of "near-miss" vehicular incidents. Because drivers with untreated sleep apnea may cause a large number of preventable automobile accidents, physicians have specific duties involving these drivers. First, physicians must try to identify impaired drivers with sleep apnea before they have an accident; routinely asking patients about loud snoring and hypersomnolence may help identify these impaired drivers. Second, physicians must consider the diagnosis of sleep apnea when examining patients who fall asleep while driving. Next, physicians must warn their patients with sleep apnea about the risks of driving with untreated sleep apnea. Finally, physicians must treat any seriously impaired driver with sleep apnea and keep these patients from driving until they can receive successful treatment.