The workload of a local hospital-based drug information centre over a 5-year period was studied and was related to the utilisation of primary reference sources in reply to drug related inquiries.Doctors used the service more often than any other health care professional group and questions relating to drug administration/dosage, choice of drug, adverse effects and pharmaceutical problems accounted for over 50", of the total number of inquiries. Over the study period there was an upward trend in the number of inquiries requiring the use of primary references in answering queries. Of these inquiries approximately 4 5 O were concerned specifically with drug choice and adverse drug reactions. The results demonstrate the significant contribution of a drug information service to patient care, the interdependence of the pharmaceutical, medical and nursing professions and the need for drug information centres to expand their role into determining drug-use policies and the collation of adverse drug reaction reports. In addition, useful primary reference sources for the provision of drug information services have been identified and guidelines for the selection of appropriate journals have been given. T h e creation of in-house evaluated drug information literature is recommended.