The prevalence of detectable blood alcohol in all new adult patients attending an accident and emergency department was 10.3%. The mean concentration was 20.9 mmol/1 (96 mg/dl). There were significantly more patients with detectable alcohol in the following groups: male patients; patients aged under 35 years; patients attending on Saturdays; patients attending between 21.00 and 08.59 hours; patients involved in road traffic accidents; patients presenting because of drug overdosage, and head injuries. Those with detectable blood alcohol were more likely to be admitted, probably because of their associated reason for attendance. Patients referred by their general practitioner were less likely to have detectable blood alcohol.