In order to understand the relation between body temperatures and activities in the elderly, sublingual temperatures and activities of daily living (ADL) of 92 elderly people living in nursing homes were measured in the winter of 1989 and 1990. Thermal conditions in the three nursing homes were also measured simultaneously. In two nursing homes, where most of the people of low ADL lived, room temperatures were usually kept above 20 degrees C during most of the day, while in the remaining home, where many of the people of high ADL lived, room temperatures in the morning decreased to 8 degrees C. In spite of the better thermal conditions, mean sublingual temperatures, measured in the morning, of the low ADL group were significantly lower than that of middle and the high ADL groups. Moreover, the prevalence of low body temperatures (< 35.5 degrees C) was higher in the low ADL group than in the other two groups. From these results it appears that investigations of the living environment for older people should be widened.