Excessive and inappropriate use of antibiotics in hospitals contributes to the development of antibiotic resistance and higher costs. At Aker University Hospital the use of antibiotics and the associated costs have increased over the last years. In an attempt to reverse this trend we introduced guidelines for prescribing antibiotics, based on knowledge of the local pattern of resistance. The programme resulted in a reduction of 9% in the use of antimicrobial drugs and of 24% in the associated costs, i.e. a saving of NOK 2.2 million in one year. From 1995 to 1996 there was a further reduction in antibiotic consumption by 7%. We conclude that guidelines for use of antibiotics, and relevant information, can be useful tools in influencing the prescription of such drugs.