To determine the proportion of methicillin-resistant Staphylococcus aureus (MRSA) among patients presenting for hospitalization and to assess risk factors for MRSA carriage, we conducted a study for 13 months at five Pittsburgh-area hospitals. Of 504 S aureus identified, 125 (25%) were MRSA Independent risk factors for MRSA included organ transplantation, employment in a healthcare facility, pressure sores, tube feeding, and hospitalization within the preceding year.