Records of motor vehicle accidents occurring over an eight-year period were used for the identification of all drivers killed in accidents involving neither other vehicles nor pedestrians. The resulting group of 117 drivers included 87 who died within four hours of their accidents. Postmortem determinations for alcohol were performed in 83 (95%) of these 87 cases. Of these 83, forty-one (49%) were found to have had blood alcohol levels of 0.15% or more at death; and an additional 17 (20%) were found to have levels between 0.05 and 0.15%. There is justification for assuming that any driver with a blood alcohol level of 0.15% or more is incapable of driving safely and that this is also true of many drivers with levels in the 0.05 to 0.15% range. It is therefore concluded that the use of alcohol was probably a causal factor in one half or more of the deaths which resulted from accidents of this type.