Techniques suitable for the isolation of human cardiac cells have previously been reported. However, there are difficulties concerning the reliability and reproducibility of the available methods. In the present study, a technique developed for the isolation of canine cardiocytes was successfully applied to allow isolation of human atrial and ventricular myocytes from small samples of myocardium. Application of this method allowed a direct comparison of the ionic currents recorded from human atrial and ventricular myocytes with those recorded from other mammalian preparations.