On October 25, 2000, the Mississippi State Department of Health (MSDH) notified CDC that, since November 1999, 31 inmates had acquired methicillin-resistant Staphylococcus aureus (MRSA) skin or soft tissue infections at a state prison. During November 1998-October 1999, no MRSA infections had been reported at the prison, which houses approximately 1,200 female and 1,800 male inmates. This report summarizes the case investigation and the nasal culture prevalence survey conducted by MSDH and CDC during November 2000. Findings indicate that MRSA infections were transmitted person-to-person within the prison, and that the number of asymptomatic carriers was unexpectedly high for a nonhealth-care setting. Correctional facilities can reduce the increasing prevalence of MRSA disease by identifying and appropriately treating infected persons and by instituting prevention measures.