This study investigated the effects of pyridostigmine pretreatment, NBC protective gear, and heat-exercise exposure on psychomotor performance and subjective sensations in eight healthy male volunteers. Exercise in heat enhanced performance of vertical addition (+7.3%, p < 0.001) but prolonged the reaction time (+4.4%, p < 0.01). The effects of pyridostigmine, protective gear, and the interactions between the various stressors were not significant. Cognitive performance was not dependent on body core temperature. Multiple complaints of subjective discomfort arose from wearing the protective garment. The results suggest the existence of a significant subjective discomfort but an absence of major cognitive decrements in a multiple-stresses state of chemical warfare alertness.