Detailed descriptions of cardiac geometry and architecture are necessary for examining and understanding structural changes to the myocardium that are the result of pathologies, for interpreting the results of experimental studies of propagation, and for use as a three-dimensional orthotropically anisotropic model for the computational reconstruction of propagation during arrhythmias. Diffusion tensor imaging (DTI) provides a means to reconstruct fibre and sheet orientation throughout the ventricles. We reconstruct and quantify canine cardiac architecture in selected regions of the left and right ventricular free walls and the inter-ventricular septum. Fibre inclination angle rotates smoothly through the wall in all regions, from positive in the endocardium to negative in the epicardium. However, fibre transverse and sheet angles show large variability in basal regions. Additionally, regions where two populations (positive and negative) of sheet structure merge are identified. From these data, we conclude that a single DTI-derived atlas model of ventricular architecture should be applicable to modelling propagation in wedges from the equatorial and apical left ventricle, and allow comparisons to experimental studies carried out in wedge preparations. However, due to inter-individual variability in basal regions, individual (rather than atlas) DTI models of basal wedges or of the whole ventricles will be required.