On 1 January 1989, in an effort to reduce diversion of benzodiazepines for illicit use and reduce inappropriate prescribing, a regulation was implemented requiring the reporting of all benzodiazepine prescriptions to the New York State Department of Health. To assess the impact of the regulation on prescribing practices to the elderly, we followed the number of benzodiazepines and other central nervous system medications prescribed to a cohort of participants in an elderly pharmaceutical insurance program. Benzodiazepines were prescribed for 4652 (22%) of the 20,944 patients studied. By the last quarter of 1989, benzodiazepines were prescribed for 3120 (15%) patients, a decrease of 33%. The number of prescriptions of benzodiazepines decreased by 5010 (45%), from 11,123 to 6113. Decreases in the number of prescriptions were similar across benzodiazepine brands (range 40-56%). Statistically significant (p < 0.05) decreases were seen in all sex, age, race and marital status groups. Increases in number (and percent increases) of prescriptions for miscellaneous anxiolytics (i.e. hydroxyzine (399, 69%), meprobamate (299, 149%), buspirone (263, 111%), chloral hydrate (138, 265%), antidepressants (658, 19%), barbiturates (150, 29%), and tranquilizers (198, 19%), some of which may be more toxic or less effective, were noted. New York State's reporting regulation was effective in reducing both the number of patients being prescribed benzodiazepines and the number of prescriptions given to those who remain on benzodiazepines in the elderly population studies.