a b s t r a c t Occupants' thermal sensations, perceptions and behaviors in buildings with split air-conditioners in hot-humid area of China were systematically investigated for a whole year with longitudinal design. Thirty college students, naturally acclimatized to local climate and well experienced with the indoor envi-ronments of buildings, participated in the present study. They reported their thermal sensations, perceptions and behaviors in questionnaires while their ambient environmental variables were measured. A close match of indoor and outdoor climate was found. Thermal sensation was found to be a linear function of ET* or SET and thermal neutrality was 25.6 C in ET* or 24.9 C in SET. The central five categories of the ASHRAE 9-point thermal sensation scale were found to be acceptable and the 90% (80%) acceptable range of thermal environment was found to be 20.6e30.5 C (16.9e34.2 C) in ET*. The adaptive behaviors of clothing adjustment, opening windows and using fans were found to be closely correlated with indoor ET*. The split air-conditioners were used from May to October and turned on most often at midnight with indoor air temperature of 30.1 C and setting temperature of 26.1 C. Compared with those from naturally ventilated buildings, the occupants from buildings with split air-conditioners kept indoor climates much cooler, used adaptive opportunities much earlier and perceived their ambient environments more sensitively and rigidly.