The Amazon is a giant piece of "amphibian" land which is the result of complex geological and evolutionary processes. The number of living beings in such a land is difficult to estimate. The interactions between these organ­ isms and the environment are fascinating but barely understood. These features lured us to the Amazon in 1981. However, soon after, we realized that the dimensions of these interactions were overwhelming. This book is designed to review aspects of the physiology and biochemistry of fishes of the Amazon. The description of the pulsative nature of the environment and the distinct features of the ichthyofauna of the Amazon were central to the main goal. Nevertheless, any complete view is limited by the magnitude of the intraspecific variability coupled with the complex fluctuations of the environment. Thus, we have placed an emphasis on respiratory physiology and biochemistry. The reference list was made as complete as possible, particularly regarding special publications not readily available. We hope that this book is useful for comparative physiologists, tropical biologists, and the people interested in interactions between organ­ isms and their environment. We are grateful to many people who contributed to the making of this book. Our initial ideas were influenced by Drs. Arno Schwantes, Maria Lufza Schwantes, Jose Tundisi, Anna Emflia Vazzoler, and Naercio Menezes.