A three-year prospective study of 3,180 non-dementia persons in Sendai City, Japan was conducted to examine the effects of physical status and diseases diagnosed on dementia incidence. This cohort had been made at the initial survey in 1988 and the evaluation for incident dementia was performed on 2,461 respondents (77.4%) in a follow-up survey in 1991. Regarding physical status, the logistic regression including sex, age, health status, ambulatory activity and activities of daily living indicated that the poor health status and the limitation of ambulatory activity were significantly associated with an increased risk of dementia. The significant positive association with dementia was observed on stroke, respiratory disease and depression. This study identified the high risk population for dementia in the aspect of physical status.