The impact of alcohol on injury patterns was studied by using 14,920 injured men aged 15-64 years seen in an emergency room in Helsinki, Finland. Blood alcohol was estimated by clinical evaluation and breath test, and was coded into a three-grade intoxication code. Intoxication was recorded in 19.7 per cent. Head injury was more common among the intoxicated (64.1 per cent) than among the sober (17.6 per cent). The odds of head injury, if 1.0 among the sober, was 8.3 among the intoxicated. This head injury effect (HIE) was found in every major external cause category: falls 15.4, traffic 3.0, other unintentional injury 3.4 and assault 2.6. A major difference in HIE was found by hospitalization status: 2.1 for hospitalized and 9.8 for ambulatory patients. Alcohol seems to produce mostly low-energy events (like falls) resulting usually in minor, though potentially dangerous, head injury.