While evidence exists that a person's peripheral temperature responds to his state of arousal or stress, it also responds to other environmental factors. Wrist temperature has been found to vary with ambient temperature, and to increase during the school day. Before wrist temperature can be established as a valid measure of anxiety, stress, or arousal, extraneous variables must be identified and their effects minimized. To address this issue, a study was conducted which examined the effect on wrist temperature of ambient temperature, outside air temperature, time of the school day, and grade level differences among students. On 9 days from November to February, 19 sixth graders, 17 seventh graders, and 18 eighth graders strapped on Bio-Temp wrist bands used to measure their wrist temperatures. Readings were taken at 8:40, 8:50, 9:00, 11:30, and 2:40 during the school day. Careful measurements were also made of ambient and outside temperatures. Analysis of data revealed a systematic increasing trend for mean wrist temperature from the earliest reading to the latest for every grade level. The mean wrist temperatures for all students were "corrected" for the point in the circadian thermal cycle, for shared variation with ambient temperatures, and for the warming of the wrist when coming into the classroom from the outside. A model for explaining wrist temperatures was developed. (NB)