The 12-lead electrocardiogram during sinus rhythm was studied in 20 patients with arrhythmogenic right ventricular (RV) dysplasia with symptomatic ventricular tachycardia. Findings were analyzed, together with echocardiographic evaluation of site, extent and progression of RV wall abnormalities. Electrocardiographic abnormalities were found in 90% of patients. No correlation was found between abnormalities on the initial 12-lead electrocardiogram, and the echocardiographic extent and location of RV involvement. Over time, echocardiographic progression of the disease was observed; RV size increased in 6 of 7 patients from 34 +/- 3 to 39 +/- 3 mm (p = 0.01), and there was progression in the extent of RV wall motion abnormalities in 4 of 7 patients. Analysis of serial electrocardiographic recordings did not reveal changes indicative of progression of the disease during follow-up of 71 +/- 48 months. It is concluded that electrocardiographic abnormalities suggesting arrhythmogenic RV dysplasia are present in 90% of symptomatic patients on the first electrocardiogram recorded during sinus rhythm. However, serial electrocardiographic recordings in these patients do not provide information regarding anatomic progression of the disease.