Each year approximately 1,500,000 people experience acute myocardial infarction. About 40% of them die, half before they reach the hospital. Ventricular fibrillation (VF) is a major cause of cardiac arrest, and delay in administering antiarrhythmic agents contributes to the incidence of out-of-hospital deaths. The 3 antiarrhythmic drugs currently used by paramedics for cardiac arrest are bretylium, lidocaine, and procainamide. The early use of bretylium tosylate is stressed in Advanced Cardiac Life Support protocols because of the agent's antifibrillatory properties, that is, its ability to increase the VF threshold and to block reentry. Evidence indicates that early, aggressive use of bretylium tosylate as a first-line agent improves the likelihood of successful resuscitation. Preliminary data are presented from an ongoing comparative study of prehospital use of bretylium tosylate and lidocaine for VF. One hundred seventeen cardiac arrests have occurred, 55 of which were associated with VF and are included in the study. Resuscitation was not attempted in 3 of the 55 patients at the request of the family and physician. Of the remaining 52 patients, 17 received bretylium tosylate plus lidocaine, 12 lidocaine alone, and 7 only bretylium tosylate. There were 16 patients who did not receive medications. According to the study protocol, the choice of antiarrhythmic agents was determined by the paramedic shift during which arrest occurred. Of the 52 patients treated, 16 (30%) survived. It is too soon to draw any conclusions.