International Review of Research in Mental Retardation is an ongoing scholarly look at research into the causes, effects, classification systems, syndromes, etc. of mental retardation. Contributors come from wide-ranging perspectives, including genetics, psychology, education, and other health and behavioral sciences. *Discusses the developmental epidemiology of mental retardation and developmental disabilities*Explores the cutting edge methodological, statistical, and theoretical advances within the field*Section I serves as an introduction, Section II reviews the various measurements, and Section III focuses on the epidemiological findings