The purpose of present study was to investigate the physiological characteristics of sociopsychological stress induced by the communication box method. In this method, the nonfoot shocked rats were used as the psychologically stressed experimental group. In acute stress experiments, nonfoot shocked rats were exposed to emotional responses from foot shocked rats for 6 h in the light (0900-1500) or in the dark phase (2100-0300). In the light phase, the induced increase in plasma corticosterone levels of nonfoot shocked and foot shocked rats returned to corresponding control levels 6 h following the initiation of stress session, whereas those in the dark phase were significantly higher. Although there were some differences in corticosterone responses between both phases, the acute effect of sociopsychological stress was unclear. Chronic stress experiment with daily exposure for 1 h to sociopsychological stress caused the plasma corticosterone levels of nonfoot shocked rats to increase significantly not only in the postexposure level (just after stress exposure) but also in the preexposure level (before stress exposure) when naive rats were used daily as foot shocked animals. These results suggest that the repeated exposure of sociopsychological stress can induce physiological changes, and stressful situation can be established with only emotional responses from foot shocked rats.