Work involved during the preflight preparation of spacecraft involves the handling of materials that are very toxic to humans. These toxins attack the respiratory and skin system and, therefore, impose the requirement for full suit enclosures. The weight, structure, and operating parameters of such a suit can be expected to have a significant effect upon the metabolic and thermal responses of user , especially in high workload situation and ambient temperature extremes.This paper discribes the testing of the operational version of the Propellant Handler's Ensemble (PHE). In particular, parameters affecting the physiology or the user were measured during a work-rest regimen performed in three temperature environments: -7, 23, and 43 C (20, 74, and I10 F). Six subjects performed tests in these environment, in two versions of the PHE, the autonomous backpack version and the hoseline supplied configuration. Measurements included heart rate, four skin temperatures, rectal temperature, oxygen and carbon dioxide in the helmet area, suit pressure, and interior suit temperature. It was concluded that the weight and configuratin of the suit significantly influenced the physiological stress on the user. The weight, at 29.5 kg (65 lb) for the PHE and backpack, proved to be a primary stressor, as indicated by elevated heart rates. The high workload portion of the protocol also taxed the limit of the environmental control unit because of the increased respiratory requirements. Oxygen levels dropped as much as 4 below resting levels and the carbon dioxide level increased by a similar amount. Finally, thermal stress is clearly evident, especially in the 43 C (110 F) tests. Stale-of-the-art design techniques in whole body suits do not provide solutions to these problems. Therefore, it has been necessary to institute operational restrictions and impose medical and physical standards to avoid situations that could adversely affect the well-being of the worker.