Impaired driving is an important road safety problem, and the characteristics of drivers impaired by alcohol or drugs are relevant to targeted interventions. This study considers young drivers' sociodemographic attributes: age, sex, class of origin and educational attainment, based on a national cohort of young Swedish drivers (1988-2000) followed up in police registers for their first motor vehicle crash. Of all crashes reported for these drivers, 946 were where the driver was suspected of being under the influence of alcohol or other substances (corresponding to 6% of all first crashes). Impaired driving significantly increases the odds of severe and fatal injuries, regardless of sociodemographic attributes. Observed differences in the proportions of impaired drivers reveal significant excess risks among males, persons aged 18-19, those from households classified as "workers" and "others" (including, e.g. the long-term unemployed and those on long-term sick leave), and those with low educational attainment. Impaired driving is a risk factor in all sociodemographic strata among young people. Members of some groups are more likely to be found than others among impaired drivers on occasion of first motor vehicle crash.