Progress in treatment of cardiac arrhythmias is not confined to electronic devices. Pharmacology continues to make significant contributions. Prominent among the newer drugs for ventricular rhythm disturbances is lidocaine, which is rapidly replacing its less satisfactory analogue, procaine amide. Lidocaine also depresses myocardial irritability, prolongs conduction time, depolarization time, and the refractory period. But unlike procaine amide, it rarely causes deleterious side effects such as severe hypotensive reactions with an accompanying fall in cardiac output. Encouraged by reported effectiveness of lidocaine in preventing ventricular fibrillation in dogs under hypothermia, surgeons began using the drug for mechanically induced cardiac arrhythmias during operations on the heart. Hitchcock and Keown1 used it in 500 patients. Weiss2 reported conversion of ventricular arrhythmias to sinus rhythm during closed cardiac surgery in 126 out of 148 (85.2%) patients. He administered a single intravenous injection of 2% in a dosage range of 1 mg/0.9 to