Work performance of mask wearers has been shown to be less than performance of the same individuals without masks. How much this performance decrement is attributable to psychological factors was the subject of this study. This experiment was designed to give quantitative information about the effect of anxiety level on relative work performance while wearing a respirator mask. Twenty subjects were tested for trait anxiety levels and performed on a treadmill at 80-85% of their maximum heart rates until they reached voluntary end-point. Physiological, metabolic, and subjective measurements were taken every minute. While experimental variability precluded many of the results from achieving statistical significance, performance times with the mask averaged less than without the mask. Anxious subjects experience more discomfort, perform for shorter times, and accomplish less total work than their lower anxiety counterparts, even when rate of work can be adjusted.