Objective: The aim of this study was to evaluate the epidemiology of Stenotrophomonas maltophilia infections in the Gazi University Hospital. Material and Methods: The incidence, clinical characteristics, antimicrobial susceptibility patterns and outcomes of nosocomial S. maltophilia infections during a five years period (2003-2007) were retrospectively analyzed. Results: Eighty-nine cases with nosocomial S. maltophilia infection were enrolled in the study. S. maltophilia was identified from 1.6% of the nosocomial isolates. S. maltophilia infections were seen mostly in intensive care units (ICU) and the hematology department. Nosocomial S. maltophilia infection incidence was 0.6 per 1000 admissions. Pneumonias were the most common nosocomial infections, followed by bloodstream infections. The crude mortality rate was 50.6%. Stay in ICU, increased age, prolonged hospitalization, using invasive procedures, and the presence of pneumonia were significantly higher in fatal cases. The most active antimicrobial agents against S. maltophilia were trimethoprim-sulfamethoxazole, ciprofloxacin, and cefoperazone-sulbactam. Conclusions: The incidence of S. maltophilia infections did not significantly change during the study period. The mortality rate was higher in ICUs. Pneumonias were the most common nosocomial infections with a high mortality rate. The high resistance rates for many currently available broad-spectrum antibiotics and its known association with prior antibiotic use indicates the importance of rational antibiotic use and regular infection surveillance in the hospital, especially in ICU settings.