The Metropolitan Atlanta Developmental Disabilities Study is the first US, population-based epidemiologic study of the prevalence of mental retardation, cerebral palsy, hearing impairment, and visual impairment among school-age children. The study population consisted of children who were 10 years of age between 1985 and 1987 and whose mothers were residents of the five Georgia counties of Clayton, Cobb, DeKalb, Fulton, and Gwinnett at the time of the child's birth. Since children with developmental disabilities are identified by and receive services from various health, social service, and education systems, a multiple-source case identification method was used. This study is unique in that individual school records were used to identify children with the four disabilities. Use of a multiple-source method made it possible to confirm specific conditions and to classify subtypes of disabilities. About 95% of the children with one or more of these four disabilities were initially identified through the school systems. This approach is much less costly than conducting medical and psychologic assessments on populations of children. In addition, this method made it possible to estimate accurately the "administrative prevalence" of these disabilities (ie, the number of children previously identified with these disabilities for the purpose of providing services). The prevalence rates found in this study, per 1000 10-year-old children, were as follows: mental retardation, 10.3; cerebral palsy, 2.0; hearing impairment, 1.0; and visual impairment, 0.6.(ABSTRACT TRUNCATED AT 250 WORDS)