Electrocardiographic follow-up was conducted for 17 patients with hypertrophic cardiomyopathy including six cases who received left ventriculographic follow-up. 1. Serial ECG changes were as follows: 1) In seven patients negativity of the T wave appeared or increased concomitantly with increased voltage of SV1 + RV5 (A-1 group). 2) In four patients, negativity of the T wave decreased or disappeared with the decreased voltage of SV1 + RV5 (A-2 group). 3) In six patients, there were insignificant changes of both T wave and SV1 + RV5 (B group). 2. Results of serial left ventriculography and biventriculography were as follows: 1) Two patients (A-1 group) showed an increased voltage of SV1 + RV5 (25 mm----48 mm, 42 mm----54 mm), and increased thickness of the apical wall (10 mm----12 mm, 8 mm----11 mm) and the anterior wall (13 mm----16 mm, 10 mm----16 mm). However, the thickness of the posterior and interventricular septal walls did not change. The configuration of the end-diastolic left ventriculogram (RAO 30 degrees) changed from a round configuration to the so-called "beak" configuration. 2) Two patients (A-2 group) showed a decreased voltage of SV1 + RV5 (81 mm----26 mm, 73 mm----53 mm), decreased thickness of the apical wall (18 mm----10 mm, 21 mm----15 mm) and the anterior wall (12 mm----9 mm, 17 mm----12 mm). The end-diastolic left ventriculogram changed from a spade-like configuration to a round configuration. In the analysis of diastolic function measured by digitized cineangiograms using a picture-analyzer, diastolic dysfunction was already present at the initial observation. The diastolic and systolic dysfunction progressed during serial observations. These patients showed the clinical pictures of dilated cardiomyopathy at the final observation. 3) Two patients with no remarkable changes of the T wave (B group) showed insignificant changes in configuration of the left ventriculogram and wall thickness. In conclusion, serial changes in configuration of the left ventricle and wall thickness, especially of the anterior and apical walls, are compatible with the serial changes of the ECG in hypertrophic cardiomyopathy. The patients whose negative T waves decreased or disappeared had diastolic dysfunction at the initial observation, and deterioration of both diastolic and systolic dysfunctions during serial observations.