Although an extensive body of literature exists on Head Start, only a small part of this literature is program impact research. The body of existing research is inadequate in size, quality, and comparability for use in drawing conclusions about the impact of Head Start in any area in which Head Start provides services. This report from the General Accounting Office (GAO) provides an examination of the research plans of the Department of Health and Human Services (DHHS). Planned research will focus on new or innovative service delivery strategies (including descriptive studies, studies of program variations and demonstrations, and studies of the quality of innovative programs) but will provide little impact data on regular Head Start programs. DHHS believes effectiveness of Head Start is already proven, that conducting impact studies would be difficult and perhaps unethical, and that national estimates of program impact and comparisons with other service providers are not appropriate. GAO concluded that the increasing demand for shrinking federal resources and for accountability points to the need for conducting impact studies on Head Start and recommended that GHHS include in its research plan an assessment of the impact of regular Head Start programs. A summary of DHHS' comments conclude the report. Six appendices document how the GAO report was developed: Appendix 1, "Objectives, Scope, and Methodology"; Appendix 2, "Research, Demonstration, and Evaluation Budgets for the Head Start Program"; Appendix 3, "Summaries of Studies Included in the Review"; Appendix 4 "Comments from the Department of Health and Human Services"; Appendix 5 Acknowledgments"; and Appendix 6, "GAO Contacts and Staff Acknowledgments." (DR)