This study investigated the hypothesis that an individual's maximal oxygen consumption can be realistically predicted by the maximal time achieved in the Balke or Bruce treadmill protocols. The range of maximal oxygen consumption that can be expected for healthy individuals of any given age and activity was also evaluated. The maximal oxygen consumptions achieved by 79 men exercised using the Balke protocol and 77 men using the Bruce protocol were linearly regressed by a least-squares fit technique on maximal treadmill time and on age with activity status classified. Statistical analysis demonstrated an inadequate relationship for predicting maximal oxygen consumption from maximal treadmill time using either protocol. Also, maximal oxygen consumption correlated poorly with age even though activity status was considered. These findings make the nomogram for predicting an individual's functional aerobic impairment a clinical technique of questionable value. Since maximal oxygen consumption can only be grossly estimated from the maximal time performed in the Bruce or Balke protocols, there is no necessity to use them in preference to other clinically acceptable protocols.