Field surveys were conducted at an office with multinational workers in Japan to investigate the differences in the way groups of occupants perceive the environment under real working conditions. Returned questionnaires, 406 in total, were classified into three groups according to their nationality and sex. Only 26% of workers reported their working environment to be comfortable. A significant neutral temperature difference of 3.1 degreesC was observed between the Japanese female group and the non-Japanese male group under their usual working conditions. Japanese females reported a higher frequency of sick building syndrome related symptoms compared to other groups. Occupant comfort and reported frequency of SBS symptoms were closely related to deviation of the thermal sensation vote from neutral. The thermal environment was found to be a major factor affecting occupant comfort in the concerned office. Differences in the perception of the indoor environment were negatively affecting the ratings of their working environment.