In this study, the effects of mood state on taste sensitivity was evaluated in humans who exposed to condition of mental or physical fatigue and tension. Taste responses to quinine sulfate (bitter), citric acid (sour) and sucrose (sweet) were tested. The intensity of the taste sensations were recorded by a computerized time-intensity (TI) on-line system. Subjects performed mental tasks by personal computer or physical tasks by ergometer. Before and after these sessions, the sensation of taste were recorded by the TI system, and in addition, psychological mood state were evaluated with POMS (Profile of Mood State). TI evaluation showed that after the mental tasks, the duration and total amount of taste were reduced in all taste. Furthermore, the maximum intensity was reduced only in bitterness. There were no changes in bitterness and sweetness sensations following physical tasks. However, relative to before the physical task, only the sensation of sourness was reduced by physical task. We also studied the mechanism of the changes of taste sensation by analysis of saliva components.