Purpose: Methicillin resistant Staphylococcus aureus (MRSA) infections are frequent in intensive care units (ICUs). This prospective study was implemented to investigate the frequency of MRSA colonization on admission to ICU. Materials and methods: This study was conducted at Erciyes University Faculty of Medicine Gevher Nesibe Hospital Internal Medicine ICU from December 2004 to January 2006. All patients admitted to ICU were included in the study. Nose, axilla and groin swab cultures were carried out within 48 hours of ICU admission then cultivated on mannitol salt agar including 6mg/L oxacillin. Results: A total of 408 patients were followed up during the study. MRSA colonization on admission was detected in 23 (5.64%) patients. MRSA infection was detected in 5 (21.7%) of those colonized patients. Staying in hospital before ICU admission, length of stay in hospital before ICU, previous antibiotic use, duration of previous antibiotic use, decubit ulcers and central venous catheter were statistically significant (p<0.05). Comorbidities, age, sex, APACHE II and SOFA scores were not determined as risk factors. Conclusion: The patients colonized with MRSA before admission to ICU are important sources of MRSA outbreaks. Detection of risk factors may decrease the rate of MRSA infections in ICUs.