The document--one third of which consists of appendixes--presents the final report of a 3 year national study to evaluate the quality and quantity of minority participation in the developmental disabilities (DD) movement, in such areas as service recipients, planning, policy formation, administration, and decision making. Study objectives were to determine the structure and demographic characteristics of DD agencies, the extent and nature of services provided by the agencies, the characteristics of the clientele, the extent and level of participation, and the unmet needs of minority DD people. The study was divided into three parts: a series of nationwide meetings with consumers and agencies to obtain comments and recommendations to be used in developing the survey instrument, a literature review to provide additional background on trends in the movement, and a national survey of 1,200 agencies. The final report covers the history of the investigation, the literature review, major findings, methodology, data analysis, discussion of key findings, and recommendations and suggested action plans. A selected bibliography is included. Among the eight appendixes are questionnaires and a list of project resources. (DLS)