Abstract Three groups of subjects, seven subjects each, were required, to perform a central tracking task and simultaneously respond to peripheral stimuli, while being exposed to heat stress environments. One group was exposed to a 95°F and 50% RH environment, the second group was exposed to a 95°F and 75% RH environment, and the third group was exposed to a 100°F and 50% RH environment. The performance results showed that there was a significant deterioration in tracking and increase in reaction time only when the subjects were exposed to the 95°F and 75% RH environment. The peripheral field of awareness was not significantly affected by any of the three environments.