To determine the population at high risk of nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) on hospital patients admission, a nasal swab was taken from the following patients: (1) those aged 70 years or over (age >or= 70), (2) non ambulatory receiving regular home visits by nurses and physicians (visiting), (3) residents of nursing homes (nursing home), (4) patients from other hospitals (another Hp), and (5) those scheduled for surgery (presurgery). Between March and July 2000, a total of 412 patients were admitted and 136 were enrolled. MRSA was isolated from 12 (8.8%) patients. The number of patients positive for MRSA in the five groups, age >or=70, visiting, nursing home, another Hp, and presurgery, were 3 of 68, 3 of 21, 2 of 3, 3 of 9, and 1 of 35, respectively. Multivariate analysis revealed that living in a nursing home [odds ratio (OR) = 32.82, P = 0.010] or coming from another hospital (OR = 14.55, P = 0.0043) were high risk factors with for nasal carriage of MRSA. Furthermore, patients' ages were further divided into three categories, <or=79, 80-89, >or=90, and regarded as independent high risk factors (OR = 3.08, P = 0.043). The results were that advanced living in a age (>or=80, >or=90), living in a nursing home or coming from another hospital are high risk factors of nasal carriage of MRSA on hospital admission.