The discussion about underground spaces for office use has intensified during the past few decades, but the human reactions towards them are not yet well understood. Furthermore, most of the previous studies have been carried out in western countries. In the present study, Japanese office workers' psychological reactions to underground and above-ground offices were investigated with regard to the perceived importance of windows in the office, and the perceived lighting and visual conditions in the underground and above-ground offices. The study was carried out in the form of a questionnaire survey. The subjects were 22 employees in underground and 86 employees in above-ground offices. The results confirmed that windows were strongly desired in offices, especially by employees working underground and not having windows. The underground employees also evaluated their lighting condition more negatively than did the above-ground workers. Considering that type of furniture and colour scheme, as well as other environmental factors, such as type and level of artificial lighting, temperature and noise level, were very similar in the underground and above-ground offices, it is concluded that the perceived need for windows and the perception of the lighting conditions in our study was strongly influenced by psychological factors, such as the awareness of being underground. Furthermore, the Japanese subjects' reactions were similar to those of the western subjects found in previous studies, which suggests that reactions towards windowlessness and underground spaces are widespread, not influenced substantially by cultural or climatic conditions. It is, therefore, argued that underground spaces for office use should be avoided as much as possible. If underground space utilization is necessary, the occupants' psychological reactions should be considered to a much greater extent in the design process than is the case at present.