Military facilities provide unique opportunities for studying Staphylococcus aureus nasal colonization and transmission patterns. In this cross-sectional observational study, we assessed the prevalence of S. aureus nasal colonization among Chinese military volunteers in two camps in the Beijing area. Antimicrobial resistance patterns, risk factors for colonization, and transmission patterns using pulsed-field gel electrophoresis were also evaluated. From May to July 2007, 1,044 nasal swabs were collected from military volunteers from suburban (560) and urban (484) Staphylococcus aureus is an important cause of skin and soft tissue infections, as well as invasive infections in humans (25). Since methicillin-resistant S. aureus (MRSA) was first reported, it has become endemic in hospitals and communities around the world (10). The recent emergence of a highly virulent community-associated MRSA (CA-MRSA) and vancomycin-resistant, intermediate-resistant, or heteroresistant S. aureus further heightens public health concerns (14,17,37,46). Prevention of S. aureus infection and reduction of the spread of virulent and resistant strains are therefore of great importance.On the other hand, S. aureus is a member of the commensal microflora. The anterior nares of the nose are the primary reservoirs of S. aureus colonization in humans, and many S. aureus infections occur in persons with prior nasal bacterial carriage (47). Nasal colonization is an important step in the pathogenesis of S. aureus infection and is a risk factor for acquiring nosocomial infection (22). It has been shown that 80% of nosocomial S. aureus bacteremia episodes in carriers of this bacteria were attributed to an endogenous source (44). Nosocomial S. aureus bacteremia was three times more frequent in S. aureus carriers than in noncarriers (48). Numerous studies of S. aureus nasal carriage have been carried out in various geographic regions in the United States and the Netherlands (2,5,7,21,23,27,28,41). Cross-section surveys of nasal carriage prevalence and transmission mechanisms in special healthy populations are beneficial in assessing risk factors associated with S. aureus infections (2,8,13,26,(32)(33)(34)(35). Military facilities provide unique opportunities for studying S. aureus nasal colonization and transmission (11,19,52).In China, MRSA was shown in 63% of S. aureus isolates, among which 77% nosocomial and 43% community isolates were MRSA (49). According to a study conducted in 2005, the mean incidence of MRSA across China was over 50%, and in Shanghai, the prevalence was over 80%, contributed to by two major epidemic MRSA clones with unique geographic distribution (24,45,50,51). Therefore, understanding and controlling the spread of MRSA in both hospital and community settings in China are now of paramount importance. The majority of S. aureus isolates studied in China have been limited to clinical patients, and S. aureus isolates recovered from healthy populations or those from healthy military volunteers have not been previously reported....