In the present study a new method for evaluating left ventricular chamber compliance is reported. We induced a programmed postextrasystolic beat during routine left ventricular angiography through a temporary pacing catheter, placed at the sinoatrial junction (S1-S1 = 600 ms; S1-S2 = 400 ms; S2-S3 = 800 ms). Thirty-two patients with documented critical coronary artery disease and 5 normal subjects represent the study group. The method allows to have two couples of end-diastolic pressure and end-diastolic volume and we calculated the modulus of chamber stiffness with the formula: K = (1n EDP 3 - 1n EDP 1)/(EDVI 3 - EDVI 1), where EDP 1-3 and EDVI 1-3 are end-diastolic pressure and end-diastolic volume index in basal beat and in the postextrasystolic pause, respectively. Left ventricular chamber compliance (dV/dP) and specific compliance (dV/VdP) were also calculated. In order to assess the clinical value of the method, we divided the patients with coronary artery disease into three groups: 12 patients had angina and no previous myocardial infarction; 15 had a previous myocardial infarction and responded to postextrasystolic potentiation with an increase in left ventricular ejection fraction greater than or equal to 0.08 and 5 patients had myocardial infarction and did not respond to postextrasystolic potentiation. Diastolic indices showed significant differences between subgroups; patients with more severe disease and with systolic dysfunction had the highest values of the modulus of chamber stiffness and the lowest values of chamber compliance. Moreover, these indices were not correlated with basal end-diastolic volumes, but they were directly and significantly correlated with the actual increase in left ventricular filling.