In an effort to reduce the outbreak of highway crashes and citations observed among young males aged 18-19, countermeasure programs were conducted with seniors in 10 suburban high schools including 'driving workshops' conducted one day a week for six weeks under regular teachers trained by project staff. Records of 9,000 subjects, including control drivers from paired school districts, were followed over 18 months of treatment. Although average driving behavior did not change, young men were not indifferent to the workshops. Their accident rate rose during the first 12 months but dropped in the last six months, particularly among an 'alienated' subgroup who had poor grades and were older than their classmates. The crash rate of this alienated subgroup dropped to one-fourth the pre-treatment level. Men with good grades had stable records, and women showed neutral or adverse long-term responses. A separate program of police-sponsored assemblies had no visible effect on subsequent driving. (Author)