This study compared functional capacity during treadmill exercise testing and during bicycle exercise radionuclide angiography. 262 patients performed maximal upright bicycle exercise and also performed maximal graded exercise testing using either the Bruce (n = 158) or Naughton (n = 104) treadmill protocols. The functional capacity was well correlated between bicycle and treadmill for Bruce (r = 0.89), Naughton (r = 0.93), or combined treadmill (r = 0.90) protocols. However, the functional capacity was significantly lower during bicycle than during treadmill testing for Bruce (8.3 vs. 10.5 METs), Naughton (7.8 vs. 8.7 METs), or combined treadmill (8.1 vs. 9.8 METs) protocols. Treadmill functional capacity could be predicted from bicycle functional capacity using the following equations: Bruce METs =1.00 × (bike METs) + 2.23, Naughton METs = 0.94 × (bike METs) + 1.40, and combined treadmill METs = 0.98 × (bike METs) + 1.85.