Since the first gap junction protein (connexin) was cloned over a decade ago, more than a dozen connexin genes have been cloned. Consequently, a wealth of information on the molecular basis of gap junctional communication has been accumulated. This book pays tribute to this exciting era in the history of cell communication research by documenting the great strides made in this field as a result of the merging of biophysics and molecular biology, two of the most powerful approaches to studying the molecular basis of membrane channel behavior. Twenty-eight comprehensive chapters, authored by internationally recognized leaders in the field, discuss the biophysical, physiological, and molecular characteristics of cell-to-cell communication via gap junctions. Key aspects of molecular structure, formation, gating, conductance, and permeability of vertebrate and invertebrate gap junction channels are highlighted. In addition, a number of chapters focus on recent discoveries that implicate connexin mutations and alterations of gap junctional communication in the pathogenesis of several diseases, including the X-linked Charcot Marie Tooth demyelinating disease, some forms of inherited sensorineural deafness, malignant transformation, cardiac malformations and arrhythmia, eye lens cataract, and Chagas’ disease.