This volume presents some of the most exciting recent advances in the area of osmoregulation, from the control of gene expression to whole animal response. In particular, the differences and similarities in the drinking response between a number of vertebrate groups including both aquatic and terrestrial organisms are discussed. This volume will be of interest to all those working in the fields of marine and freshwater biology, comparative physiology and endocrinology and molecular biology of ion transporters and water channels. This book is in the Experimental Biology Reviews series (also known as SEB Seminar Series).