The purpose of this thesis was to examine; the effects of various stressors on human thermoregulation and immune function, a functional link between these two systems and the potential of novel measurement techniques. A valid, un-obtrusive measure of skin temperature was desirable for a majority of studies in this thesis. Wireless iButtons® provided such a method. Both iButtons® and conventional thermistors displayed high validity correlation (r > 0.999) and mean bias (iButtons® = +0.121°C, thernistors = +0.045°C) with a reference thermometer. A reliable measure of in vivo immunity in response to stressors, was also desirable. Contact sensitization with diphenylcyclopropenone proved a simple and robust method. Results demonstrate that exercise-induced-stress impairs both phases of in vivo T-cell-mediated immunity (oedema: induction -53%; elicitation -19%). Two-nights total sleep deprivation, with or without energy-restriction did not impair thermoregulation during cold exposure, nor appear to increase the risk of hypothermia. Core temperature, skin temperature and time to reach 35.9°C core temperature were not significantly different between trials. Three-nights sleep disruption (SDIS) did not affect core temperature at rest or during exercise-heat-stress. However, SDIS upper-body skin temperature was higher during exercise and forearm-sweating lower (-21%). Thus, alterations to heat-loss pathways were observed, but with no increase in thermal strain. Concurrent examination of the effects of SDIS, demonstrated enhanced in vivo T-cell-mediated immunity (oedema +98%). In vitro markers were unaltered by SDIS, suggesting these markers may not reveal the true effect of stressors on the co-ordinated immune response. Significant differences between sleep deprivation and control proximal and distal skin temperatures lends evidence to the functional, mechanistic coupling between circadian variations in skin temperature and skin immunity, as prolonged periods of increased skin blood flow observed during sleep disruption provides enhanced maintenance of skin immunity and thus likely to account for the observed increase in T-cell-mediated immune responses. The purpose of this thesis was to examine the effects of various stressors on thermoregulation and immune function, and to examine the functional link between these two systems, utilizing conventional, as well as examining the potential future usage of novel techniques and methods in humans.