The pattern of cardiac arrhythmias and their treatment, by propranolol and chlordiazepoxide, during the first 48 hr of alcohol withdrawal has been studied. Prior to treatment, the incidence of serious and life-threatening arrhythmias was found to be very low and uncorrelated with most biochemical parameters. Propranolol treatment, while efficacious in controlling arrhythmias, was limited due to its association with hallucinations. Chlordiazepoxide was associated with poor early control of arrhythmias. The combination of propranolol and chlordiazepoxide was found to perform best overall with substantial reductions in arrhythmias and the fewest treatment failures.