Abstract: Since the application of acupunctural anesthesia to surgical operation in Chinathe problem of pain has become the main subject in interdiciplinary researches. Thestudy of the characteristics and roles of pain which is considered as a psychologicalprocess is one of the main tasks in psychology. In ancient China there were ideas somewhat akin to that of modern biologicalrhythms. Guided by these concepts thus we begin to study the periodic changes ofhuman cutaneous pain threshold in the acupunctural anesthesia practice since 1975. The results suggested that there were a "6 months circannual rhythms in the hu-man cutaneous pain threshold with the first peak in March (the mean value of reac-tion time was 600.6±110.6 centiseconds) and the second peak in Sept. (the meanvalue was 605.5±76.7 centiseconds). The two lowest phases of rhythmic changes ina year occured in June and Jan. with the mean value of 454.4±26.3 centisec. and435.9±60.8 centisec. respectively. There were significant difference (p<0.001) be-tween each two adjacent measurung in all four measurements. There were 81.9% ofcases showed changes of cutaneous pain threshold with a 6 months circannual rhythms. The supplementary experiment (the experiment for correlation between skin tem-perature and pain induced by thermal stimulation) suggested that the change ofcutaneous pain threshold was not solely dependant on the change of skin temperature.As a psychological reaction pain seems to have a 6 months circannual rhythms itself.The reason remains to be further investigated.

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