In a double blind study performed in cooperation with 69 emergency doctors and general practitioners in the catchment areas of the university and of the city hospital in Lübeck the action of intramuscular lidocaine on mortality and on the incidence of arrhythmias was investigated in patients with acute myocardial infarction aged less than 70 years. The mortality in the lidocaine group was significantly lower than in the placebo group. The incidence of ventricular arrhythmias up to 120 minutes after the lidocaine injection was also lower than in the placebo group. However, the only case of primary ventricular fibrillation was in the lidocaine group. As the difference in mortality between the two groups appeared at a time when an antifibrillatory action of lidocaine can no longer be assumed one must question whether the positively beneficial effect was real or whether the lower mortality was in fact due to primarily milder disease in the lidocaine group.