Analyzed is the impact of regional, racial or ethnic, and socioeconomic factors on handicapped students' participation during 1973 in special education programs in more than 37,000 schools within 2,500 local U.S. school districts. Included are data on American Indian, black, Spanish surnamed, Asian American, and nonminority pupils enrolled in programs for the educable and trainable mentally retarded, special disabilities such as physical handicaps and specific learning disabilities, slow learners, and the severely emotionally disturbed. Noted among major findings are correlations between special education participation geographic locale (such as that overall participation is highest in the South and lowest in the West), minority pupils' enrollment (such as that minority pupils in general and black pupils in particular participate at a much higher rate than their nonminority counterparts), and socioeconomic influences (such as that special education participation rates tend to be higher in districts which are smaller, less urban, poorer, and enroll predominantly black students). A section on additional findings includes information on national projections, special school enrollments, local service distribution, additional socioeconomic variables (such as percentages of Title I revenues), and alternate data analysis techniques. Also discussed are policy implications, recommendations for further research (including the need to reexamine current special programing efforts), major data sources analyzed, and technical analysis approaches. Two separate appendixes contain extensive graphical information. (LH)