This study was undertaken to examine the effect of cardiac assist and left ventricular function after dynamic cardiomyoplasty (DCMP). In the first group (GI) of 10 mongrel dogs DCMP was drived immediately after wrapping both ventricles by latissmus dorsi muscle flap (LDMF). In the second group (GII) of 10 mongrel dogs DCMP was derived over 6 weeks after production of DCMP for achievement of complete adhesion between LDMF and myocardium. In the both groups, aortic pressure, cardiac output, left ventricular systolic pressure, and ejection fraction of the left ventricle were significantly increased by DCMP driving (p < 0.001). But left ventricular systolic pressure was remarkably increased in GII compared with that of GI (21.2 +/- 10.2% versus 14.0 +/- 9.6%, p < 0.001), and end diastolic pressure of the left ventricle was apparently decreased in GII (61.6 +/- 42.3% p < 0.05). Thus, satisfactory results were recognized that cardiac assist for left ventricular function was enhanced after completion of adhesion between myocardium and LDMF. Echocardiography in GII demonstrated that left ventricular systolic dimention was significantly decreased from 33.8 +/- 1.0 mm to 27.6 +/- 1.2 mm (p < 0.001). Thus, left ventricular fractional shortening was significantly increased from 24.0 +/- 2.4% to 38.0 +/- 2.6% (p < 0.001). However, left ventricle end-diastolic dimention was not changed even during DCMP driving. So disturbance in left ventricular function during diastole could not be recognized. In conclusion, especially after adhesion of both muscles of LDMF and myocardium, effect of cardiac assist was remarkably enhanced, and disturbance of diastolic function of the left ventricle could not be observed.