To assess the effect of alcohol intoxication on injury severity and head injury assessment, blood alcohol concentrations (BAC) were related to the severity of injuries (Injury Severity Score and Assault Trauma Score) and Glasgow Coma Scores (GCS) in 242 consecutive victims of weekend, night-time assault, none of whom had head injuries. No correlation was found between degree of intoxication and severity of injury. There was a highly significant correlation between BAC and GCS. However, high BACs (greater than 240 mg/100 ml) were associated with only a 2-3 point reduction in GCS. The median BAC in patients with a normal GCS was 115 mg/100 ml. Neurological assessments need to take account of the highly variable, depressive effects of alcohol.