The pattern of endemic pathogenic isolates and the rates of acquisition of methicillin-resistant Staphylococcus aureus (MRSA) were evaluated in our 22-bed ICU during a SARS outbreak. This period was characterized by a change in patient case-mix, high use of steroids, change in the pattern of antibiotic prescribing, upgrading of infection control precautions, and wearing gloves all the time. These changes were associated with an increase in the isolation of MRSA, Candida and Stenotrophomonas species. On the other hand, Pseudomonas and Klebsiella species, which used to be endemic, had disappeared. The MRSA ICU acquisition rate was significantly increased during SARS (25.3% vs 5.0% in 2000, 3.8% in 2001, 2.9% in 2002, P < 0.001). This showed that changes within an ICU during a SARS outbreak could lead to a change in the pathogen pattern, and a significant increase in MRSA acquisition.