To start with, we feel that we should explain why the book has been entitled Cholera Toxins. In fact, the enterotoxin secreted by Vibrio cholerae, which is p- marily responsible for causation of the disease, is conventionally known as or referred to as cholera toxin, or CT. By using the word toxins (in its plural form), we wanted to cover all of the different types of toxins-and not just CT-produced by V. cholerae. We could have used the title Toxins of Vibrio cholerae, but we believe that Cholera Toxins is simpler and equally as expressive. However, due to its relative importance, the story of CT covers most of this book. Also, compared to all other toxins of V. cholerae, CT has been investigated more extensively. This book was jointly written by us. It is not a multiauthor book in which each expert writes one chapter. In that respect our task is harder. On the other hand, it has given us the unique opportunity to present the entire subject in the way that we conceived it. Besides, our objective is to cater to the needs of not only active research scientists but also students from different disciplines-microbiology, molecular physiology and pharmacology, basic medicines, etc. -and as such, we have attempted to present the subject in a way that will be appreciated by general readers. Further, we have provided some information that students and predoctoral researchers may find useful at the end of the book.