The primary goal of the U.S. Environmental Protection Agency is the reduction of risk to public health and to the environment. Within this context, the Office of Research and Development (ORD) provides the scientific information necessary to determine the extent of these risks and to develop and evaluate technology options to reduce, eliminate or prevent them. As part of this process ORD must anticipate the scientific questions that will arise so that appropriate data may be obtained and evaluated for the regulatory decision-making process. The framework for this document is a series of scientific issues identified by EPA's six topical Research Committees: Water, Air and Radiation, Hazardous Waste, Interdisciplinary, Multimedia Energy (including acid deposition), and Pesticides and Toxics. These committees, composed of representatives of ORD, Agency Program (regulatory) Offices and the Regions, are jointly chaired by senior managers from ORD and the appropriate Program Office. The critical scientific issues for each committee were delineated in a joint strategy document by the Assistant Administrators of ORD and the appropriate Program Office. Thus, these issues reflect the perspectives of both the regulatory and research offices of EPA on determining where scientific uncertainties lie and how the Agency might reduce those uncertainties. The integration of the overall research program is, thus, a matrix of topically-oriented research committees and discipline-oriented offices.