Using a Critical Incidents approach, 600 drivers were called upon to identify the bases of decisions to drink and drive. In an unstructured interview, each driver descnbed the bases for decisions leading to specific instances of impaired driving, including decisions regarding participation in drinking events, transportation to events, plans prior to and following initiation of drinking, activities while drinking, leaving the drinking event, and transportation following drinking. Over 12,000 individual decision bases were descended. While the bases were highly specific to the individual decisions, those involving the social environment exerted the strongest influence, followed in decreasing order by influences of a personal nature, the occasion giving rise to drinking, economic considerations, plans already made, and usual patterns of behavior. Results evidenced the need for 1) friends, hosts and sellers of alcohol to avoid inadvertent encouragement to over-consumption of alcohol and driving while impaired, 2) better planning in providing alternatives to drinking as well as driving, and 3) helping drinkers and those around them to redefine what they perceive as their "responsibilities" with respect to situations leading to alcohol impaired driving.