The purpose of this study was to evaluate antibiotic usage in Selcuk University Hospital. Files of 600 patients were investigated for antibiotic usage and frequency. Antibiotics had been used in 394 (65.7%) of the patients. Infection had been diagnosed in 39.6% of these patients by clinical findings and in 3.0% by microbiological tests. In 53.1% of the patients antibiotics had been used for prophylaxis. In 4.3% of the patients the reason for antibiotic usage was not understood. The most common used antibiotics for prophylaxis were cefepime and meropenem, and durations of surgical prophylaxis were longer than proposals in guidelines (mean 6.4 days). These results show that the use of antimicrobial drugs the hospital where the authors work must be controlled, and that the communication between clinics and clinical microbiology laboratories must be reorganized.