40 patients seen in general practice and psychiatric outpatient clinics who had taken lorazepam or diazepam alone in regular dosage for a mean period of 3.6 years had their benzodiazepine replaced by propranolol (60--120 mg/day) or placebo for two weeks under double-blind conditions. Depending on the criteria for the definition of an abstinence syndrome, 27--45% of the patients had withdrawal symptoms during the study. Propranolol did not affect the drop-out rate or the incidence of withdrawal symptoms but significantly reduced their severity in patients completing the study. The percentage fall in serum levels of desmethyldiazepam in patients who experienced withdrawal symptoms after stopping diazepam was significantly greater in patients with no withdrawal symptoms.