It has long been recognized that people with identifiable congenital causes of developmental disabilities display peculiar patterns of behavior and temperament. An explosion of new information in the field of so-called behavioral genetics has precipitated a need for a book describing behaviorial phenotypes. The book consists of three parts: Part I opens with an account of the evolution of behaviorial genetics in developmental disability. The second part covers measurement and research methodology and includes chapters on various types of self-injurious behavior that occur in different phenotypes and a chapter on Fragile X--a model for inquiry into behavioral phenotypes. The sections on genetic analysis are particularly useful to clinicians who are unfamiliar with contemporary genetic techniques. Part III summarizes behavioral phenotypes of over thirty biologically distinct conditions.