Forty patients with hypertrophic cardiomyopathy were investigated by Doppler echocardiography for intraventricular blood flow abnormalities. None had a bundle branch block. The patients were recruited on the basis of the presence of at least one of four different types of abnormal left ventricular blood flow movements during systole, isovolumetric relaxation, and diastole (time after mitral valve opening). The abnormal blood flow patterns were composed of the following: (1) systolic left ventricular outflow and midventricular obstruction in 20 of 40 and in 6 of 40 patients, respectively; (2) retrograde isovolumetric relaxation flow (IVRFretro; mean velocity, 0.7 +/- 0.3 m/sec), that is, flow toward the apex of the left ventricle, in 28 of 40 patients; (3) antegrade isovolumetric relaxation flow (IVRFante; mean velocity, 1.6 +/- 1.0 m/sec), that is, flow toward the left ventricular outflow tract, in 3 of 40 patients; and (4) diastolic antegrade flow (DFante; mean velocity, 0.9 +/- 0.3 m/sec), that is, flow opposite to mitral inflow, in 10 of 40 patients. There were significantly fewer patients with asymmetric septal hypertrophy (group 1) than with apical hypertrophic cardiomyopathy (group 2) showing DFante (1/29 versus 9/11, p less than 0.01). IVRFretro and DFante revealed higher velocities in patients with marked left ventricular asymmetric hypertrophy than in those with mild hypertrophy. Thus, in hypertrophic cardiomyopathy and especially in patients with marked asymmetric hypertrophy, there are different types of abnormal intraventricular blood flow movements during isovolumetric relaxation and disatole. This phenomenon is probably caused by asynchronous relaxation of the asymmetrically distributed, hypertrophied myocardium. DFante is more often observed in the apical cardiomyopathy than other forms of hypertrophic cardiomyopathy probably attributable to apically localized left ventricular cavity obliteration.