After an infectious disease specialist (IDS) was introduced into a community teaching hospital, the use of antibiotics in eight of the main hospital departments was considerably reduced. The average daily expenditure on antibiotics before the IDS was appointed (April-June 1984) was $5.6. This was reduced in the last quarter of the study (April-June 1986) to $1.6. A drastic change, from $7.6 to $2.0, was noted in the surgical departments, due mainly to a strict policy in the prophylactic use of antibiotics. The success of the IDS was achieved by a combination of educational programmes, co-operation of the microbiology laboratory and the hospital pharmacy as well as by limiting restrictions to an extent that maintained clinical efficacy and the goodwill of those concerned.