Long QT syndrome (LQTS) is a prime example of interplay between molecular biology, cellular physiology, and organ physiology. Both the congenital and acquired forms of LQTS are due to intrinsic and / or acquired abnoma1ities of the ionic currents responsible for cardiac repolarization. We analyzed the QTc interval, QRS axes and interventricular septal thickness (IVST) in 41 patients who had a prolonged QT interval on routine electrocardiography (ECG) (5 females and 36 males, mean age 65 ± 13 years). The QRS axis of patients in the LQTS group (27 ± 49°) was significantly lower (p < 0.05) than in the control group (46 ± 26°). However, the IVST in the LQTS group (10 ± 2 mm) was significantly thicker than in the control group (9 ± 1 mm) (p < 0.05), while the WTd was not significantly different. The QTc interval in patients with ventricular septal hypertrophy (IVST ≥ 12 mm, 478.8 ± 7.9 msec) was significantly longer (p < 0.05) than in the normal group (IVST < 12 mm, 472.1 ± 17.5 msec). In conclusion, the results of this preliminary study suggest that prolongation of the QT interval on ECG should prompt screening for electrocardiographic evidence of ventricular hypertrophy in patients with this disease.