We report, in conjunction with other findings, the evolution of the dispersion of QT and QTc in patients who for the last 7 years have been treated with enalapril for systemic hypertension with left ventricular (LV) hypertrophy. Twenty-four essential hypertensive patients who had received no previous treatment took enalapril (20 mg twice daily) for 7 years. In a pretreatment placebo phase and 8 weeks and 1, 3, 5, 6, and 7 years after the start of therapy, cardiovascular parameters were determined by two-dimensional guided M-mode echocardiography, and the QT interval and corrected QT interval (QTc) and their dispersions were obtained from amplified standard 12-lead electrocardiograms. Therapy rapidly reduced blood pressure (BP) from 156/105 mm Hg to normal values; at 7-year follow-up, BP was 130/84 mm Hg (p <0.001 with respect to the placebo phase). LV mass index decreased progressively until at 5-year follow-up the reduction had reached 39% (p <0.001), after which neither LV mass index nor any structural parameter underwent any further significant change. LV pump function was also significantly better after 7 years of treatment. During this time, QT and QTc decreased significantly, as did the dispersion of both QT (from 61+/-21 to 37+/-14 ms) and QTc (from 67+/-27 to 41+/-16 ms). We conclude that long-term enalapril treatment of hypertensive patients with LV hypertrophy not only induces marked regression of LV mass and improved LV systolic function, but also reduces the dispersions of QT and QTc, which probably reduces the likelihood of ventricular arrhythmias and improves prognosis.