The activation sequence on the epicardial surface of the in vivo rabbit ventricle has been recorded and analyzed under conditions of normal sinus rhythm and controlled hemodynamic load. Data for the analysis was gathered sequentially using a personal computer PC-based 32-channel data acquisition system that was connected via a switching system to pressure and flow transducers and an epicardial sock containing 120 electrodes arranged in cylindrical coordinates of 8 rows and 15 columns. The adequacy of temporal and two-dimensional spatial sampling was analyzed, providing the theoretical basis for the application of (1) various digital signal processing methods for conditioning the data, and (2) a Fourier method for constructing high resolution epicardial isopotential and isochronal contour maps. These maps provide a useful tool for analyzing the spatial and temporal aspects of ventricular epicardial activation. Observed patterns of excitation were compared and found to correlate with the results of anatomical studies of the specialized conduction system.