Aims : To analyse the relationship between oral bacteria and the health and functional status of the elderly. Methods and Results : The bacteria species in the oral cavity of the elderly were examined. It was found that the bedridden subjects staying at two hospitals for long-term (HOBR) showed significantly lower detection rates of commensal bacteria species and significantly higher detection rates of Pseudomonas aeruginosa , of methicillin-resistant Staphylococcus aureus (MRSA) and of coagulase(-) Staph. aureus than those living independently (the independent). In addition, the detection rate of Haemophilus parainfluenzae in NUBR was discovered to be higher than that found in the independent. In HOBR, the detection rate of Ps. aeruginosa was significantly higher among in-patients who required continual care than those in need of partial care, while the detection rate of MRSA was significantly higher among in-patients with low serum albumin than those with normal serum albumin. Conclusions: Oral bacteria examination analysis proved that the risks of infection of some pathogenic bacteria species were correlated with functional status, physical function and nutritional state. Significance and Impact of the Study: Our study suggests that the oral bacteria, especially pathogenic bacteria were influenced by the functional status of the elderly and the type and quality of the facilities for the bedridden, physical function and nutritional state.