BACKGROUND: Propafenone is a new class Ic antiarrhythmic compound.This study was performed to evaluate the clinical efficacy and safety of propafenone by double-blind, placebo-controlled, randomized cross-over comparison of propafenone and disopyramide in patients with stable ventricular ectopy. METHODS: All patients were included in the study if they had an average of at least 30 PVC/hr on a 24-hour Holter recordings. During the 1st 7 days, two placebo tablets(identical in apperance to the propafenone and the disopyramide tablets) were administrated in a double-blind manner(run-in period). Then 1st treatment period lasting 1 week with one verum and the other placebo, wish-out period of 3 day,2nd treatment period lasting 1 week with cross-over drugs were followed. RESULTS: Twenty patients were enrolled. During the run-in period, VPCs were reduced to 18%, compared to the baseline data before the administration of placebo.During the treatment period,propafenone 600mg/day reduced VPCs by 43% and disopyramide 400mg/day reduced VPCs by -10% Propafenone was effective(80% or greater reduction of VPCs) in 7 of 20 patients. Disopyramide was not effective in all patients. Propafenone and disopyramide produced no significant change of paired VPCs and VT events. Propafenone had no effect on heart rate. It increased the PR interval(7.9%;p<0.01) and QRS interval(5.2%;p<0.01). The drug did not change QTc interval(-1.1%) significantly. There were no cardiovascular side effects. Propafenone produced nausea in one patient. Disopyramide produced dysuria in 2 patients. CONCLUSIONS: Propafenone was more effective in controlling VPC than disopyramide, and there was no major limiting side effects.