Data from two pharmaceutical marketing research data bases, the National Prescription Audit and the National Disease and Therapeutic Index, were used to study outpa tient use of prescription sedative-hypnotic drugs in the United States from 1970 through 1989. Retail pharmacies dispensed an estimated 62.5 million prescriptions for sedative-hypnotic drugs in 1970. This number declined by half to 31.6 million in 1978. This decline has continued, so that in 1989 there were 20.8 million dispensed prescrip tions. From 1970 to 1989, barbiturate and nonbarbiturate nonbenzodiazepine prescriptions decreased 24-fold and 18-fold, respectively, and benzodiazepine prescriptions in creased 26-fold. By 1989, the ultrashort-acting benzodiaz epine drug triazolam was the leading sedative hypnotic, with about 40% of the total sedative-hypnotic market in the 6 years since its marketing. Data also indicate shifts from longer to shorter acting, and from higher to lower dose, benzodiazepine prescriptions, increasing use of antidepres sant drugs for insomnia, female predominance of use, and increasing use with age. (Arch Intern Med. 1991;151:1779-1783)