This double-blind study involved the continuous (six to 22 weeks) treatment of 180 chronically anxious outpatients with diazepam, 15 to 40 mg/day. Our findings indicate that a significant number of patients benefit from prolonged diazepam treatment and that tolerance to the anxiolytic effect of diazepam does not develop during a 22-week study period. The duration of continual treatment with sedative-benzodiazepines was clearly the most important determinant of withdrawal reactions. Patients treated continuously for less than eight months with sedative-benzodiazepines had an incidence of withdrawal of 5%, whereas 43% of patients treated for eight months or more demonstrated clear withdrawal reactions. While these withdrawal reactions produced considerable distress, they were neither life threatening nor incapacitating and did not include convulsions or psychotic reactions. In all cases, withdrawal reactions could be readily managed by gradually tapering the dose of the benzodiazepine.