Most attempts to quantitate myocardial function rely on morphologic features of complex pressure waveforms to reflect the functional properties of the ventricular myocardium. Relationships between waveform components and the function of the organ generating them were examined in 38 rhesus monkeys by harmonic analysis of left ventricular pressure waveforms. In the basal state, harmonic content was closely correlated (r=0.98) with hemodynamic state, as quantitated by heart rate, systolic and diastolic pressures, left ventricular end-diastolic pressure and maximum contractile element velocity. Hemodynamic indices were expressed as significant linear functions of harmonic terms (r=0.71--0.83), in patterns consistent with the principle of superposition. In 20 animals, infusions of dextran, methoxamine, propranolol or ouabain were used to further assess this relationship. Results demonstrated (1) significant correlation between changes in hemodynamic and harmonic parameter (4= 0.99), (2) correlations between each harmonic term and the set of hemodynamic indices such that specific terms varied directly with contractility but not with loading, whereas others correlated significantly only with loading, and (3) that the patterns in these correlations were of such specificity as to permit construction of significant discriminant functions (p less than 0.0001) that accurately characterized the pharmacologically induced hemodynamic change in 85% (56/67) of trials.