The purpose of this study was to understand the indoor thermal environment, especially with regard to humidity, in 12 homes for elderly in the Niigata prefecture, Japan. The study was made over the four seasons, with temperature and humidity measurements and reports. This chapter describes the structural condition of the houses, the health condition and daily behavior of the residents, various air conditioning situations, and the thermal environment of the houses through all the seasons. The following results were obtained: (1) the large difference in the residents' living styles was apparent in the operation and control of the cooling and heating equipment; (2) differences in globe temperatures were small at daybreak through all seasons and large at night time in the autumn and winter; (3) the inside and outside, and vertical temperature differences were smallest in the summer, and largest in the winter; (4) the indoor thermal environment is influenced by the operating conditions of heating equipment and the room layout, in addition to the effects of thermal insulation and air tightness of the house; (5) most residents vote the neutral or the satisfactory evaluation.