The increasing number of fatalities and serious injuries due to motor vehicle accidents makes the prevention of these accidents an important public health problem. It is estimated that the 40,000 deaths and 1,250,000 injuries each year cost over four billion dollars. The three major factors involved in motor vehicle accident prevention are the road, the vehicle, and the driver. The human element, the major factor in accidents, has been neglected. The medical factors may be divided into three main categories: (1) organic, (2) psychologic, (3) drugs. The importance of these factors is discussed. The role of the physician in motor-vehicle-accident prevention is demonstrated by the reduction in accidents resulting from a comprehensive medical program. The program consists of: 1. detailed preplacement examination, 2. periodic medical examinations, 3. study of absences due to illnesses and accidents. This program resulted in a reduction of accidents from 6377 in 1946 to 2568 in 1953 and 3130 in 1955, a decrease of over 50%. The importance of the physician in evaluating physical qualifications of vehicle operators is emphasized. The need for research to determine the relationship of specific organic disabilities and psychologic states to accident causation is stressed.