In recognition of the importance and somewhat controversial nature of the oxidant control problem, the U.S. Environmental Protection Agency (EPA) organized and conducted a five-day International Conference in September 1976. The one hundred or so presentations and discussions at the Conference revealed the existence of several issues and prompted EPA to sponsor a followup review/analysis effort. Specifically, this followup effort carefully and impartially reviewed and analyzed relevant evidence and viewpoints reported at the International Conference (and elsewhere) and attempted to resolve some of the oxidant-related scientific issues. The review/analysis was conducted by non-EPA, non-industry experts of widely recognized competence and experience in the area of photochemical pollution control. The first part of the overall effort, reported here, is an explanatory analysis of the problem and definition of key issues, as viewed within the research component of EPA. Following, will be the reports of the expert/reviewer groups offering either resolution of issues or recommendations for additional research needed to achieve such resolutions.