OBJECTIVES: To assess the effect of a comprehensive, educational antibiotic management program designed to improve antibiotic use and reduce treatment costs in elderly patients with suspected urinary or respiratory tract infection. DESIGN: Interventional cohort study with 12 cross-sectional drug utilization reviews of antibiotic use before, during, and after the multifaceted intervention. SETTING: A 304-bed university hospital for geriatric patients. PARTICIPANTS: A total of 3,383 elderly patients. INTERVENTIONS: An educational program including distribution of guidelines on the diagnosis and treatment of urinary and respiratory tract infections; lectures on geriatric infectious diseases; weekly ward rounds for patients with suspected infection; and targeted, individual counseling on diagnosis and antibiotic treatment of infections. MEASUREMENTS: Antibiotic utilization data were collected from the patients' records. Antimicrobial costs were calculated using 1998 hospital wholesale prices. RESULTS: Of 3,383 screened patients, 680 (20%) received at least one antibiotic. During the study period, the mean number of prescribed drugs per patient increased from 5.9 to 7.6 (29%; P<.001). In contrast, a reduction of 15% was observed in the proportion of patients exposed to antibiotic agents (P=.08) and a drop of 26% in the number of antibiotics administered (P<.001). This resulted in a 54% decrease in cumulative daily antibiotic costs. In 83 (75%) of 110 surveyed patients, the guidelines were correctly implemented. The intervention had no measurable negative clinical effect. CONCLUSION: A comprehensive, multifaceted educational program for treating urinary and respiratory tract infections in the elderly was a safe and practical method to change physicians' antibiotic prescribing practice and significantly reduce the consumption and costs of antibiotics in a geriatric hospital.