Purpose / Context – To clarify the association between the indoor environment of residential build-ings and cerebrovascular disease, an epidemiological survey of elderly persons living in three areas of Japan that have different rates of death due to cerebrovascular disease was conducted. Methodology / Approach – This paper describes field measurements of indoor temperatures and blood pressure of 30 elderly persons during one year. Results – In almost all houses in Japan, indoor temperature differences between a living room and non-heated spaces, such as the bedroom, corridors and lavatory, during heating times are large, and the indoor temperature at daybreak can be as low as the outdoor temperature. Key Findings / Implications – The systolic blood pressure of elderly persons is positively associated with exposure to temperatures lower than 15°C. Originality – The findings of this study will contribute to the knowledge regarding the association between the indoor thermal environment and health.