AIMS: To examine patterns of drinking in the UK Armed Forces, how they vary according to gender and other demographics, and to make comparisons with the general population. DESIGN: Large cross-sectional postal questionnaire study (response rate 60%). SETTING: United Kingdom. PARTICIPANTS: A random representative sample of the regular UK Armed Forces who were in service in March 2003 (n = 8686; 7937 men, 749 women). Comparisons were made with the general population of Great Britain. MEASUREMENTS: Alcohol consumption was assessed using the Alcohol Use Disorders Identification Test (AUDIT). FINDINGS: Sixty-seven per cent of men and 49% of women in the UK Armed Forces had an AUDIT score of 8+ (defined as hazardous drinking), compared to 38% of men and 16% of women in the general population. In both sexes, for all ages, the military have a higher prevalence of hazardous drinking. Binge drinking was associated with being younger, being in the Army, being single, being a smoker and being white. Among military men, heavy drinking (AUDIT score 16+) was associated with holding a lower rank, being younger, being single, being in the Naval Service or Army, being deployed to Iraq, not having children, being a smoker, having a combat role and having a parent with a drink or drug problem. CONCLUSIONS: Excessive alcohol consumption is more common in the UK Armed Forces than in the general population. There are certain socio-demographic characteristics associated with heavy drinking within the military; for example, young age, being single and being a smoker, which may allow the targeting of preventive interventions.