To assess the relationship between blood alcohol concentration (BAC) and injury severity in an unselected population of road accident victims, case notes of 820 consecutive road accident victims presenting to hospital in a 12 month period were reviewed retrospectively. Five hundred and thirty-five of these were eligible for BAC analysis and results, obtained from the Victoria Police and the Road Safety and Traffic Bureau were available in 429 cases. These were expressed as mg/100 ml (per cent). Injury severity was quantified using the Injury Severity Score (ISS). BAC was compared with injury severity in three ways. First, Spearman's correlation coefficient (rho) of 0.27 indicated a highly significant correlation (P < 0.01). Second, the median ISS for intoxicated patients (4) was significantly higher than that for sober patients (1) (P < 0.05). Third, when patients were grouped according to ISS, the prevalence of intoxication in each group rose with increasing injury severity (chi 2: P < 0.01). We conclude that there is a significant positive correlation between BAC and injury severity in road accident victims treated at a Melbourne hospital.