A survey was carried out using the Canterbury Alcohol Screening Test (CAST) and clinical criteria for risk of alcohol withdrawal of 2000 randomly selected hospital in-patients in order to determine the prevalence of alcohol-related problems, the work-load for a specialist alcohol withdrawal service and the target group for early intervention. Patients at risk of alcohol withdrawal were followed prospectively.The major findings were: 14.3% of patients had a positive CAST and 8% were at risk of alcohol withdrawal; the prevalence of positive clinical criteria was greatest in men under the age of 30 years (OR 3.6) and very low (OR 0.34) in women over 60 years. In addition, patients who were too sick or refused to complete the questionnaire had high rates of being at risk for alcohol withdrawal. The prevalence of CAST positivity was greatest in men under the age of 40 years (OR 3.7) and lowest in women over 70 years (OR 0.2). It is concluded that 15-20% of in-patients have alcohol problems and 8% are at risk of withdrawal; questionnaires will produce underestimates of the order of 25%; and female in-patients over the age of 60 years are extremely unlikely to have problems with alcohol.