It is usually considered that isolated left ventricular hypertrophy is not responsible for marked left axis deviation, and it is associated with left anterior fascicular block. From this point of view, morphological features were studied on the vectorcardiograms recorded with the Frank's system in 63 cases. They had diseases producing systolic overload on left ventricle (mainly essential hypertension) revealed out left ventricular hypertrophy in Ecg findings. They were divided into three groups based on electrical QRS axis as follows: (ⅰ) NAD group consisted with +90°～0°. (ⅱ) LAD' group consisted with 0°～-30°. (ⅲ) LAD group consisted with -30°～-90°. The patterns of QRS Loop classified into 5 types in horizontal plane (N(Ⅰ, Ⅱ), L(Ⅰ-Ⅲ)) and 4 types in frontal plane (A～D). In horizontal plane, 75% of NAD group showed type N(Ⅰ), or N(Ⅱ), and type L(Ⅰ), or L(Ⅱ) occupied in 75% of LAD group. In frontal plane, a half of LAD belonged to type D and type A was less than 10% in LAD, compared that type A was observed in 85% of NAD. Left ventriular hypertrophy with marked left axis deviation was classified into three types on the base of QRS loop as follows: the terminal portion of QRS loop directed superiorly to the left (type B) and superiorly to the right (type C), and the majority of QRS loop located to leftward and superiorly (type D). It was considered that the electrical force caused by hypertrophied left ventricle directed more posteriorly and to the left in type B, and type D was the pattern added to type B with the delayed excitation in antero-lateral wall of left ventricle caused by left anterior fascicular block. On the other hand, it was considered that the majority of type C, showing type N(Ⅱ), was the resultant of the delayed excitation in postern-basal portion of ventricles and was not closely related with left ventricular hypertrophy or left anterior fascicular block.