Lignocaine was administered intravenously to 36 patients with acute myocardial infarction. A bolus of 100 mg followed by an infusion of 2 mg/minute failed to maintain plasma levels above 2 microgram/ml. A bolus of 100 mg followed by 4 mg/minute also failed to maintain satisfactory plasma concentrations during the first hour of therapy. A bolus of 75 mg was combined with an infusion of 10 mg/minute for 20 minutes followed by 1.5 mg/minute. Satisfactory plasma concentrations during the first hour were observed in 94 per cent of the estimations. No important adverse side effects occurred during the infusion of 10 mg/minute.