Usually, an initial step in determining accumulated O2 deficit is the estimation of the O2 demand of high intensity exercise by extrapolation from VO2 measured during steadystate submaximal exercise. It was hypothesized that O2 deficit could be determined without the need to estimate O2 demand by extrapolation. Ten women performed all-out cycle ergometer exercise tests at each of four power outputs selected so that exhaustion would occur after 90 to 600 s. Power output (W), accumulated VO2 (ml), and time to exhaustion (s) were measured in each test and then fit to the following equation: O2 deficit (ml) = O2 demand (ml.min-1.W-1).time (min).power (W) - accumulated VO2 (ml). This procedure generated values for two parameters (O2 demand and O2 deficit) for each subject. The O2 deficit was also calculated for each individual using conventional methods. The values for O2 deficit obtained using the two methods were correlated (r = .96, p < .01), and the value obtained using the experimental method tended to be larger, t(9) = 2.15, p = .06. It is concluded that O2 demand and O2 deficit can be determined from the results of several high-intensity tests without the need to extrapolate from submaximal exercise to estimate the O2 demands of supramaximal exercise.