The field of catheter ablation has grown In a rather helter-skelter fashion. Ablative techniques were applied in patients before basic bioelectric and cellular electrophysiologic effects were fully defined. Since the introduction of this technique into clinical medicine in 1982, happily, a wealth of basic information has become available, and it was thought prudent to summarize existing data in the form of a text. The purpose of this text is to provide for a concise summary of both the basic and clinical experiences to date. It was simply not possible to include chapters from many workers who have made outstanding contributions in this area. For this, I offer my profound apolo­ gies. I do wish, however, to acknowledge the outstanding work of Drs. Bharati and Lev who provided us with a sound understanding of the histolo­ gic effects of various energy delivery systems. Their seminal observations allowed us to bring this technique to clinical fruition.