This book offers one of the most comprehensive reviews written by a large number of experts in the field of development of polymeric membranes for polymer electrolyte membrane fuel cell (PEMFC). Readers of the book will feel tremendous enthusiasm that is caused when social necessity for alternative energy sources is combined with intellectual curiosity of researchers. The topics hence cover a very wide range, from the membranes developed in a large scale by industries to those developed in the academic laboratories. This book is unique since it is the first book exclusively dedicated for fuel cell membranes. The book is written for engineers, scientists, professors, graduate students as well as general readers in universities, research institutions and industries who are engaged in R & D.