The impact of institutionalization on the carriage of multiresistant bacteria among the elderly was assessed prospectively by comparing the carriage rate in institutionalized patients over 70 years of age to the carriage rate in patients over 70 living at home (58 patients/group). Nares, skin, and rectal swabs were obtained within 24 h of admission to the hospital. Among the 20 carriers identified, 75% came from institutions. Significantly, institutionalized patients were incontinent (P < 0.001), less autonomous than those living at home (P < 10(-6)), and had taken antibiotics recently (P < 0.02). The primary characteristics associated with bacterial colonization were institutional living (P < 0.02), having at least one underlying disease (P < 0.001), dependence (Karnofsky index < or = 50; P < 0.02), recent treatment with antibiotics (P < 0.02), and the presence of skin lesions (P < 0.02). Among the risk factors identified, institutionalization can be readily determined upon admission; systematic communication of carrier status of transfer patients would improve overall patient care.