In this study a total of 219 patients who developed nosocomial infections and were treated in Sisli Etfal Training and Research Hospital between January 2001 and March 2003 were evaluated retrospectively. In all, 337 bacterial strains were isolated in these patients. The aim of our study was to assess the causative agents of catheter-related nosocomial infections, the distribution rate of causative agents due to hospital units, infection sites and catheter types, and determine the risk factors which facilitate such nosocomial infections. The most frequently isolated causative agents in catheter infections were Pseudomonas spp. (17%), Klebsiella spp. (16%), E. coli (13%), Acinetobacter spp. (12%), Coagulase Negative Staphylococci (CNS) (11%) and Methicillin-Resistant S. aureus (MRSA) (9%). In 136 (59%) patients infections were due to urinary catheterization and in 52 patients (23%) due to tracheal aspiration catheters. Of the 229 catheters applied, the polymicrobial infection rate was found to be 24% (55 patients). Multiple drug resistant strains were more frequently isolated in Intensive Care Units (ICU). It was emphasized that as ICUs are important risk factors for the development of catheter infections, the resistance patterns of the isolated microorganisms from the unit should be taken into consideration for the selection of appropriate antibiotics. We also conclude that it is important to avoid unnecessary catheterization and that preventive measures should be properly applied.