To analyze the effects of the characteristics of the systolic anterior motion(SAM) of the mitral valve on the left ventricular outflow pressure gradient and to determine the relation between the anatomical characteristics of the left ventricle and the left ventricular outflow pressure gradient, mitral valve and left ventricular M mode echocardiogram and continuous wave Doppler echocardiogram of the left ventricular outflow tract were recorded in 7 patients with hypertrophic obstructive cardiomyopathy(HOCM), aged 19 to 66 years(mean 37 years). Mitral-septal distance at the closest apposition(S-SAM;1.1±2mm), duration of mitral-septal apposition(89±20 msec), time interval from the peak of the R-wave to initial apposition of the mitral valve against the interventricular septum(R-SAM interval ; 222±32 msec) and left ventricular posterior wall thickness(LVPWT; 1.1±0.5mm) were observed on mitral valve and left ventricular M-mode echocardiograms and peak flow velocity in the left ventricular outflow(V-LVOT; 3.5±1.5 m/sec) was measured from the Doppler echocardiograms of the left ventricular outflow tract.