In the first edition of Bioelectricity, Plonsey and Barr provided an introduction to electrophysiology following a quantitative approach. In this second edition they address new discoveries in the field of ion channels. The text is an introduction to electrophysiology utilizing a quantitative approach. It describes the principles of electrical fields, using basic principles from science and engineering while taking the biological applications into consideration. The book thus provides an introduction to the quantitative description of underlying electrophysiology with illustrative application to cardiac electrophysiology and functional electrical stimulation. The book can be used as a bridge to more advanced texts, particularly those that stress a quantitative approach.