With the widespread application of solid tissue and bone marrow transplantation as a treatment for an array of life threatening disorders, there is a pressing need for clinicians and experimentalists to understand the basis of immunological rejection of tissue transplants. While much previous work focuses on characterization of antigens encoded by the major histocompatibility complex (MHC) in this process, the many histocompatibility (H) antigens encoded outside of the MHC, the so-called minor H antigens, have only recently been identified at the molecular level. This easily readable but comprehensive text is the first to put together insightful historic perspectives with up-to-date advances in the molecular genetics, biochemistry and immunobiology of minor H antigens from both experimental and clinical points of view. In doing so it provides a sourcebook particularly suited for clinicians and experimental immunologists engaged in tissue transplantation. The text recounts the progress being made on many fronts. Newer approaches have extracted molecular explanations finally allowing one to ascribe a rational molecular basis to minor H minor antigens both in rodents and humans. This understanding also paves the way to apply new genomic analyses to the problem of tissue transplantation.