in the past maximum aerobic power tests have been the standard means for measuring the trained state. recent literature, however, states that the ability to work aerobically at a high percentage of one's maximum aerobic power, referred to as maximum aerobic capacity, may be an equally effective means for indicating a person's state of training. the purpose of this study was to develop a simple technique to measure maximum aerobic capacity and relate this value to the person's state of training. twenty trained and twenty untrained subjects ranging in age from 18 to 42 years participated in the study. participants who accumulated in excess of an average of fifty cooper points per week were considered as being trained, a re-test was administered to establish the reliability of using ventilation for measuring maximum aerobic capacity. the trained participants had a significantly greater mean level of maximum aerobic capacity than the untrained participants. maximum aerobic power values correlated significantly with maximum aerobic capacity values, and maximum aerobic power and the participant's age had a significantly greater correlation than maximum aerobic capacity and the participant's age. there was no evidence that the maximum aerobic capacity test was any less efficient than the maximum aerobic power test for separating out levels of training, but the former was much easier to administer. since maximum aerobic capacity was less related to age than maximum aerobic power it might be a better test for evaluating a person's state of training.