The aim of this investigation was to evaluate the epidemiology of Stenotrophomonas maltophilia in a university hospital of Turkey. From June 2000 to December-2001, S. maltophilia strains were collected, clinical presentations were noted, and MIC determinations were performed by means of E-test. Enterobacterial repetitive intergenic consensus sequences-PCR (ERIC-PCR) was used for molecular typing of the strains. Forty-four strains of S. maltophilia were isolated from 41 hospitalized patients in a teaching hospital. The majority of specimens were from the blood and respiratory tract. Antimicrobial sensitivities of these strains were as follows: 97.7% trimethoprim-sulfamethoxazole, 15.9% ticarcillin, and 95.4% ticarcillin-clavulanate. The strains were evaluated using the ERIC-PCR method. It was of interest to note that epidemiological typing revealed three small outbreaks that were caused by a total of 12 strains. The remaining isolates generated singular DNA patterns. DNA amplification was possible in 3 8 isolates and yielded 26 different patterns in a period of 20 months, leading to the suggestion that commensal bacteria becomes selected in the presence of a suitable host.