In order to measure the effect of industry-independent information on the prescribing of benzodiazepines in general practice, 128 primary practitioners were randomly allocated to three intervention groups after stratification by year of graduation. One third of the participating physicians were forwarded written information about the indications and limitations of benzodiazepines, another third received both written and oral information, and the remaining third (the control group) obtained no information at all. A comparison of the number of benzodiazepines prescribed per 100 patient contacts with prescription before and after the intervention showed an average decrease of 3% in the control group, of 14% in physicians who received only written information, and of 24% in physicians who were given additional oral information. Post hoc pair-wise comparisons revealed a significant difference at the 1% level in the number of benzodiazepines prescribed between physicians who received both written and oral information and the control group. A follow-up survey conducted 4 weeks after the intervention showed that the oral information campaign positively affected physicians' attitudes about the value of oral drug information from an industry-independent source.