Following the first report in 1961, methicillin–resistant Staphylococcus aureus (MRSA) has progressively become a leading cause of nosocomial infections. MRSA infection may have a significant impact on patient morbidity and mortality. Limited number of studies in Saudi Arabia has attempted to investigate infection and risk factors associated with nosocomial acquired MRSA. This study was designed to estimate the hidden prevalence of MRSA at King Khalid Uni-versity Hospital (KKUH), Riyadh, Saudi Arabia and identified and described the potential risk factors for MRSA infection. The study was carried out at KKUH over a period of 12 months. All the cases of hospital acquired MRSA were included. The demographic, clinical and laboratory data of the in-fected patients were obtained. Isolation and susceptibility of MRSA were performed at KKUH microbiology laboratory. The risk factors for colonization were estimated. Informa-tion concerning hospitalization, antibiotic treatment in the previous two months, and the presence of co-morbidities were obtained. The chart of patients were reviewed daily for in-dication and duration of antimicrobial therapy. The date of discharge and the duration of hospital stay were calculated. This study revealed an MRSA prevalence of 2 cases per 1000 admission. Diabetes mellitus, multiple co-morbidities, old age, male gender, antibiotics use and I.C.U. admission were sig-nificant risk factors associated with increased prevalence of MRSA acquisition. The presently applied infection control policies at KKUH were effective in controlling MRSA infection. However more studies are suggested to further explore means of further reducing MRSA burden on health systems.