APPLICANT'S ABSTRACT: Background: Alcohol is a major cause of morbidity and mortality, much of it due to injury. About 45 % of alcohol-related deaths and 80 % of alcohol-related years of productive life lost are due to injury, and a substantial proportion of non-fatal injury is attributable to alcohol. Objectives: 1) To further quantify the association between acute alcohol exposure and the risk of injury, including the relative risk at low levels of alcohol consumption. 2) To examine the relationship between chronic alcohol involvement and injury risk, with and without simultaneously including acute alcohol exposure in the model. 3) To define the extent of confounding due to other background variables such as personality traits in the association between alcohol and injury. 4) To explore patients' attributions regarding their injury using qualitative methods. Design: A case-crossover study, in which each injured person is both a case (at one point in time) and a control (at prior times), within a population-based case control study. Setting: All three hospital emergency centers in Boone County, Missouri. Participants: Cases will be patients presenting for care within 48 hours of an acute injury. Cases will also serve as controls, with drinking on the day of injury compared to drinking the previous day, the same day of the week in the previous four weeks, and the previous 28 days. Two other controls will be matched to each case by sex, age group, and time: 1) General population controls, recruited by random-digit dialing. 2) Patients presenting to the same emergency centers with a medical illness. Analysis: Odds ratios will be calculated using conditional logistic regression. Subgroup analyses will compare groups by age and sex, and by mechanism and severity of injury. Comparison between case-control and case-crossover findings will provide an estimate of the extent of confounding by stable personal factors. Goals: The proposed study is the first major attempt to control for stable between-subject variables, such as willingness to take risks, in examining the relationship between alcohol and injury. The results may lead to important new information regarding risk at low alcohol levels, helping define "safe drinking" limits more precisely, and may contribute to a better understanding of the relative contributions to injury risk of chronic alcohol involvement and acute alcohol exposure.