The ocean is a source of unique natural products, mainly accumulated in living organisms. The c.4000 species of tunicates or sea squirts (Phylum,Chordata; Subphylum,Urochordata) are a high-potential yet under-studied source of bioactive compounds for pharmaceuticals. The secondary metabolites such as alkaloids isolated from these organisms have led to the discovery of an approved anti-tumor drug, anti-cancer drugs Yondelis(R) and Aplidin(R), as well as many others in clinical trial. There is an urgent need for more research on the bioactive compounds of marine tunicates and better knowledge about the identification and biology of these species. This is the first focused book to meet this need. The taxonomy, common name, global distribution, habitat, diagnostic features and pharmaceutical compounds (along with their activities) of 165 key species of tunicates are given, with high-quality illustrations. Contributed by scientists of both Marine Biology and Pharmacy disciplines, this book will serve as a standard reference for researchers, teachers and students of Fisheries Science, Marine Biology, Life Sciences, Biotechnology, Natural Products, and Pharmacy, and as a valuable guide for pharmaceutical companies involved in the development of new drugs from marine organisms.