This study compared end-systolic pressure-volume relationship (P/V) versus wall stress index (WS) as a tool for the evaluation of ventricular contractile state during upright isometric exercise. Both indices of contractility exhibit significant (p < 0.001) increase during exercise compared to resting values. The correlation coefficients for the two indices of contractility were r = -0.45 for exercise and r = -0.70 for rest. Both were significant at the p < 0.01 level. The correlation of the difference scores between rest and exercise as computed by both indices was low (-0.20) and insignificant. These data suggest that changes in contractility from rest to exercise as measured by one index do not reflect the pattern of individual differences that are measured by means of the other index. However, from a reliability point of view, it seems appropriate to prefer the use of P/V index over the WS index in order to determine contractile state.