Flecainide, a new antiarrhythmic drug (group 1 according to the classification after Vaughan Williams), is used in the treatment of atrial and ventricular arrhythmias. Cardiac patients are compromised by arrhythmia during operative procedure. The haemodynamic effects of 1 mg/kg b.w. flecainide compared to a placebo solution were studied randomised in 20 patients undergoing coronary artery surgery (before cannulation of the large vessels). Mean arterial pressure, PAP, PCP, PRA and TPR remained unchanged, whereas heart rate (-12%), cardiac index (-17%) and dp/dtmax (-35%) decreased significantly. Total systemic resistance increased by 14%. The results show that it is possible to use flecainide during coronary artery surgery. In patients with reduced myocardial function it should be injected carefully and a decreased dose is recommended with regard to deterioration of left ventricular contractility.