The aim of the present study was to assess the prognostic value of ECG voltages at baseline and their serial changes during follow-up in a large prospective study with standardized follow-up and strictly defined end points. Patients who were 60 years old or older, with systolic blood pressure of 160 to 219 mm Hg and diastolic pressure <95 mm Hg, were randomized into the double-blind placebo-controlled Systolic Hypertension in Europe trial. Active treatment consisted of nitrendipine, which could be combined with or replaced by enalapril, hydrochlorothiazide, or both. At the end of the double-blind part of the trial (median follow-up, 2.0 years), follow-up was extended and all patients received active study drugs (median total follow-up, 6.1 years). Electrocardiography was performed at baseline and yearly thereafter. Electrocardiographic left ventricular mass was prospectively defined as the sum of 3 voltages (RaVL+SV1+RV5), which averaged 3.1+/-1.0 mV. The adjusted relative hazard rate, associated with a 1 mV higher sum at baseline, amounted to 1.10 and 1.15 for all-cause and cardiovascular mortality and to 1.21 and 1.18 for strokes and cardiac events, respectively (P< or =0.01 for all). A 1-mV decrease in electrocardiographic voltages during follow-up independently predicted a lower incidence of cardiac events (relative hazard rate: 0.86; P< or =0.05), but not of stroke or mortality. In conclusion, electrocardiographic voltages at baseline and their serial changes during follow-up predict subsequent events in older patients with systolic hypertension.