Historically, infection with strains of methicillin-resistant Staphylococcus aureus (MRSA), which are usually multidrug-resistant, has been acquired by persons in hospitals, nursing homes, and other health care institutions. These infections are known as health care-associated MRSA infections. Community-associated MRSA (CA-MRSA) infection, which bears significant similarities to and differences from health care-associated MRSA infection, appears to be on the rise and has been described in several well-defined populations, such as children, incarcerated persons, Alaskan Natives, Native Americans, Pacific Islanders, sports participants, and military personnel. CA-MRSA infection has caused severe morbidity and death in otherwise healthy persons. Proven, reproducible strategies and programs for preventing the emergence and spread of CA-MRSA are lacking. Further surveillance and epidemiological and clinical studies on CA-MRSA infections are necessary for documenting the extent of the problem and for developing and evaluating effective prevention and control efforts.