Propagation of cardiac electrical activity is simulated in a two-dimensional sheet of cells using the cable equation and the Beeler–Reuter membrane model for ventricular muscle cells. Re-entrant patterns are produced using the original Beeler–Reuter equations and two modified versions involving changes in the calcium and sodium channel dynamics. Both stable rotating waves and irregular activity are observed. The model is shown to exhibit conduction block due to stationary repolarization fronts. The origin and properties of these fronts are described.