The book provides up-to-date summaries on the main systems of blood group antigens and MHC molecules in nonhuman primates. For each system, the human antigens are described and used as a reference for comparison with their counterparts in apes and monkeys. The emphasis is on the molecular structure of the gene products, the evolutionary pathways and presumed mechanisms by which the systems have evolved. All articles are written in such a way that they can serve as an introduction to the field for nonexperts and, at the same time, as a handbook for experts. Numerous tables, diagrams, and figures provide overviews of antigen structures and their distribution in different species and evolutionary relationships. Extensive reference lists guide the reader through the literature on each topic.