The aim of this study was to investigate the effect of different conductivity values on epicardial surface potential distributions on a slab of cardiac tissue. The study was motivated by the large variation in published bidomain conductivity parameters available in the literature. Simulations presented are based on a previously published bidomain model and solution technique which includes fiber rotation. Three sets of conductivity parameters are considered and an alternative set of nondimensional parameters relating the tissue conductivities to blood conductivity is introduced. These nondimensional parameters are then used to study the relative effect of blood conductivity on the epicardial potential distributions. Each set of conductivity parameters gives rise to a distinct set of epicardial potential distributions, both in terms of morphology and magnitude. Unfortunately, the differences between the potential distributions cannot be explained by simple combinations of the conductivity values or the resulting dimensionless parameters.