Compared with the general population, HIV-infected persons are at an increased risk for MRSA colonization. In the HAART era, prevalence estimates of MRSA colonization among HIV-infected persons have been ~4% compared with 1.5% in the general population. Risk factors for MRSA colonization among HIV-infected persons include poor immune status (e.g. low CD4 cell count), recent exposure to antibiotics, illicit drug use, recent hospitalizations, prior MRSA colonization or infection, and chronic skin disease. Recent studies have linked high-risk sexual behaviours to MRSA colonization. One study among men who have sex with men (MSM), of whom 60% were HIV-infected, found that participants colonized with community-acquired MRSA (CA-MRSA) had a significantly higher number of sexual partners. This project will explore risk factors associated with MRSA colonization or infection.