This book is an attempt to present a comprehensive view on the aquatic biogeog raphy of a small but very dynamic and complex area of the globe. Luckily, this area, called here the Levant, has attracted much interest in the past and is being increasingly studied in the present. The interphasing between the knowledge of the historical and formative processes and that of the recent distributional aspects is fairly good. The recent years saw also a widening effort which expressed itself in several symposia and monographic books. Therefore I considered it possible to treat the whole subject of the aquatic biogeography of the Levant singlehandedly rather than in the presently widespread manner of an edited book. I am keenly conscious of the shortcommings of my approach of presenting much second-hand information. Possibly this is being compensated by the fact that this book has a more coherent structure and eventually a clearer scientific message. The effort spent in synthesizing the data from the widely different sources hopefully pays off in a presentation which is more easily comprehended by the average reader. For the suspicious reader, I would recommend to read first the closing chapter of this book in which the quintescence of this book and its message is presented in a summariz ing manner.