In a study designed to evaluate the effects of an educational program and an antibiotic order form on the quality of antimicrobial drug use, a prospective analysis was conducted in the department of internal medicine of a 948-bed university hospital. Following a quality-of-use review of all consecutive courses of antimicrobial drugs prescribed during four weeks, an educational program was conducted and an antibiotic order form introduced. After four years, an identical review was performed. In the first review, 109 (31%) of 347 patients were prescribed antimicrobial drugs. Only 40% of the prescriptions were considered definitely appropriate, and 13% were considered unjustified. There was a certain degree of underutilization, and only 67% of clinical isolates were susceptible to empirical therapy. In the review performed after intervention, 164 (21%) of 796 patients were given antimicrobial drugs. Defined daily doses per 100 bed days increased from 59.8 to 72.6. Fifty-three percent of the prescriptions were judged optimal, and only 9% were judged unjustified. Ninety percent of the clinical isolates were susceptible to empirical therapy. After one year, compliance with the antibiotic order forms on a voluntary basis reached 77%, documenting 86% of antimicrobial drug costs. As a result, the antibiotic order form will be useful for surveillance, if logistic support is provided by the pharmacy. The combination of several measures leads to improved quality of use. As correctly predicted by the first evaluation, improvement in quality resulted in increased drug consumption by fewer patients and a higher cost per bed day.