In order to assess the effects of the encircling endocardial ventriculotomy (EEV) on regional left ventricular function, we cannulated seven adult mongrel dogs for cardiopulmonary bypass. Two pairs of miniature pulse-transit transducers were placed in the mid-myocardium of the left ventricle, one pair in a region that would later be encompassed by an EEV and the other pair in a region of remote normal myocardium. Pressure-dimension data were analyzed during vena caval occlusions (after volume loading) both on and off cardioplumonary bypass and both before and after performance of an EEV. The EEV results in a significant decrease in diastolic compliance of the encompassed myocardium. No significant compliance changes occurred in the control regions of the same hearts. This change in regional diastolic compliance is partially responsible for a loss of systolic excursion within the EEV-encompassed region and may help to explain the severe left ventricular dysfunction that has been observed in some patients following an EEV.