Ion channels are crucial components of living cells. They are situated in the membranes of the cell and allow particular ions to pass from one side of the membrane to the other. In recent years the patch clamp technique has allowed the activity of individual channels to be measured, and recombinant DNA technology has revealed fascinating detail on channel structure. Together, these technical advances have produced a great flowering of knowledge and understanding about the subject, itself leading to further breakthroughs in science and medicine. Ion Channels provides an introduction to this scientific endeavour. It emphasizes the molecular structure of channels as determined by gene cloning technology. This molecular approach illuminates discussions of the permeability and selectivity of channels, their gating and modulation, their responses to drugs and toxins and the human diseases caused when they do not function properly. This book is aimed at an advanced undergraduate audience. It assumes little initial knowledge yet takes the readers to the frontiers of understanding.