Twenty-eight endurance trained male volunteers, 18-41 years or age, were studied to determine whether the heart rate-oxygen consumption relationships observed during Bruce protocol stress tests were similar to those observed during steady-state exercise. In addition, maximal oxygen consumption and maximal heart rate values obtained during the stress tests were compared to predicted values. The heart rate-oxygen consumption relationship observed during the stress tests was dissimilar from the relationship observed during the steady-state exercise tests. Heart rate was round to be significantly higher during the stress tests. No significant difference was round in predicted maximal oxygen consumption and maximal heart rate and actual values obtained during the stress tests. / M.S.