The aim of this study is to reveal factors associated with both dozing off at the wheel and motor vehicle accidents (MVAs) with sleep apnea syndrome (SAS) as well as other descriptive variables for driving set as independent factors.We conducted an anonymous questionnaire survey on drivers who visited the Tokyo Metropolitan Driver and Vehicle Licensing Center in order to renew their driver's license from September 25 to 29, 2006. The survey requested information regarding self reported experience of dozing off at the wheel, MVAs, usual mileage, length of license holding period, and the participants' awareness of SAS. We obtained data from 3,236 drivers (response rate: 61.8%).The rates for previous experience of feeling sleepiness at the wheel, that of dozing off at the wheel, and that of near-miss or actual MVA due to dozing off at the wheel among the participants were 40.4%, 20.3%, and 10.4% respectively. Multivariate logistic regression analysis revealed that dozing off at the wheel was significantly associated with male gender, long-term holding of a driver's license (> or = 3, or = 10, or = 20, or = 30 years: OR = 1.85, 95%CI: 1.18-2.89), higher usual mileage (> or = 30 km per a week: OR = 1.35, 95% CI: 1.06-1.73), appearance of sleepiness shortly after starting driving ( or = 3, or = 10, < 20 years: OR = 2.10, 95% CI: 1.19-3.70), appearance of sleepiness shortly after starting driving (< 2 hrs: OR = 1.70, 95% CI: 1.30-2.24), either having awareness or diagnosis of SAS were significantly associated.Not only habituation effects and fatigue due to long driving but also SAS have a significant impact on the occurrence of sleepiness related MVAs. Moreover, early diagnosis and treatment of SAS is necessary so that we can avoid dozing off at the wheel, resulting in near-miss or actual MVA.