While expert recommendations caution against long-term benzodiazepine use in the elderly, survey data suggest increasing benzodiazepine use with age. Computerized pharmacy records of staff-model HMO were used to examine benzodiazepine prescribing. Six-month prevalence of benzodiazepine use (2.8%) and prevalence of continued use (0.7%) were lower than earlier reports. Prevalence was higher in women and increased steadily with age. Among 7012 patients beginning benzodiazepine treatment, duration of use increased with patient age, prescription by a psychiatrist (vs. primary care or medical/surgical specialist), use of higher-potency drugs (lorazepam, and alprazolem, clonazepam) and larger number of pills in the initial prescription. Individual physicians varied significantly in drug choice, initial prescription size, and likelihood of chronic use. Among 200 patients treated in primary care, the physician-recorded indication for prescription was anxiety or depression in 27%, insomnia in 20%, and pain symptoms in 38%. These findings indicate a gap between benzodiazepine efficacy research and current clinical practice.