Prophylactic lidocaine hydrochloride infusion followed by oral mexiletine hydrochloride was administered in the early post operative period to patients with poor left ventricular function undergoing coronary artery bypass graft surgery, to determine whether this decreased the incidence of ventricular arrhythmias and sudden death due to arrhythmias. Patients were randomly allocated to two groups of 50 each, the lidocaine prophylaxis group and the placebo infusion group. In the lidocaine prophylaxis group bolus dose of 1.5 mg/kg lidocaine hydrochloride was administered just before release of aortic cross clamp followed by an infusion at the rate of 2 mg/min. Oral mexiletine hydrochloride 150 mg 8 hourly was started after 24 hours and continued till discharge. The results showed that 17/50, patients developed ventricular arrhythmias in the lidocaine prophylaxis group and 22/50, in the placebo group in the first postoperative week. The incidence of ventricular arrhythmias apart from ventricular fibrillation was almost similar in both groups, 13/50, and 14/50, in the lidocaine prophylaxis and placebo infusion groups respectively. The incidence of ventricular fibrillation was 4/50, in the placebo infusion group and 2/50, in the lidocaine prophylaxis group (p < 0.05). Total number of deaths were 3 in each group. We concluded that this antiarrhythmic regimen in patients with poor left ventricular function did not decrease the incidence of ventricular arrhythmias or death due to arrhythmias in the early post operative period.