Under linearly increasing work load the point of rise of the ventilatory equivalent for oxygen (VEO = V(E)/V(O2) depends upon the degree of cardiac output increment. The latter being low, the slope of the minute ventilation (V(E) curve is correspondingly steep and that of the oxygen consumption (V(O2) curve flat. Consequently, the upslope of VEO (after an initial downslope) begins earlier in case of a poor cardiac exercise performance, and vice versa. By means of continuous measurement of respiratory data with a pneumotachygraphic system and on the basis of the values of V(O2), O2-pulse and Relative Ventilatory Equivalent (= VEO/V(O2) determined at the point of rise of VEO it was possible to divide 126 patients (mostly with coronary heart disease) into 4 groups of different cardiocirculatory capacity. These differed significantly with respect to the values measured at the point of rise of VEO as well as with respect to those related to work load. There ist good reproducibility of the values determined at the point of rise of VEO. The described method represents a rapid non-invasive means of determining different stages of impairment of cardiac pump function.