Although fertility drugs are increasing the incidence of twin births, conjoined twins remain rare at about 1 in 75,000 births. Nonetheless, they present a unique opportunity to learn about human development, as well as a challenge to medical professionals. In this book, Rowena Spencer, provides a comprehensive guide that thoroughly reviews the 20th-century literature on the subject and develops her theory of how these cases occur. After introductory chapters on history and embryology, the book presents a separate chapter for each of the eight main types of conjoined twins. Detailed descriptions of conjoined twins are accompanied by information valuable in planning surgical treatment, as well as extensive tables summarizing the available data on each type. Conjoined triplets and unusual conjoined twins receive attention in the final two chapters. Including line illustrations and photographs, this encyclopaedic book about a complex subject should be a valuable reference for the many professionals who evaluate, treat and study conjoined twins.