Interpreting the results of this study, propafenone (Rytmonorm), administered orally in a dose of 900 mg daily, was more effective than disopyramide in a dose of 600 mg daily, in the treatment of patients with complex premature ventricular contractions (PVCs). The study was performed in 12 patients, with several Holter ECG monitorings to obtain quantitative data of the effectiveness in the same patient of the new drug propafenone in comparison with disopyramide in a documented effective oral regimen. A quantitative analysis of PVCs was obtained with a computer assisted detection. Clinical effectiveness, considered as 70--80% reduction of total number of PVCs, was obtained in 8/12 patients for propafenone and 6/12 for disopyramide, or as 50% reduction with suppression of all complex PVCs (couplets, repetitive, multiform and bigeminy) was obtained in 11/12 for propafenone and 9/12 for disopyramide.