Studies were performed to assess clinical applicability and usefullness of several non-invasive indices of myocardial contractility, especially, ET/PEP, Pd/ICT and (Pd/ICT)(AO/EO). In dogs preload, afterload or myocardial contractility was altered by durgs. The ET/PEP was influenced by preload as well afterload and PdICT by afterload, respectively. A correction of Pd/ICT with preload, (Pd/ICT)/(AO/EO)showed a satisfactory correlation to Vmas even when the preload and/or afterload were altered. In clinical cases, ET/PEP, Pd/ICT and (Pd/ICT)/(AO/EO) all changed following administration of positive inotropic substances. Moreover, in azotemic cases with primary change in preload the gradient of the Frank-Sterling's curve increased progressively and the entire curve was located upwards with increase of (Pd/ICT)/(AO/EO) value. In case of high-resistance type hypertension, nevertheless, (Pd/ICT)/(AO/EO) showed a tendency to change in association with alteration of its constituent factor Pd. Since there exists no absolutely perfect non-invasive index of myocardial contractility available for clinical application as yet, it would be appropriate to make overall evaluation of myocardial contractility by combined use of several indices, with underlying pathological conditions and characteristics of individual parameters taken into consideration.