The booklet provides detailed estimates on handicapping conditions for school aged populations. The figures are intended to help the federal government validate state child count data as required by P.L. 94-142, the Education for All Handicapped Children. Section I uncovers the methodology used to arrive at the estimates, and it identifies the sources used to generate statistics as well as the methods used for developing them. Section II, the bulk of the document, presents four sets of estimates based on variation in prevalence by race and poverty level. Extensive tables depict information for each state and the United States by nine handicapping conditions: mental retardation, partial hearing, deafness, speech impairments, visual handicaps, serious emotional disturbance, orthopedic impairments, other health impairments, and specific learning disabilities. Statistics also include means, standard deviations, and minimum and maximum rates. Extensive appendixes include abstracts of data sources and papers on the epidemiology of handicapping conditions. (CL)