This research plan is being produced to document the approach that will be followed by the Western Airborne Contaminants Assessment Project (WACAP) researchers as they plan, implement, and interpret the WACAP. This plan has been reviewed by an international team of scientific experts (Seattle, December 2002), NPS staff, land managers, and policy makers and revised accordingly. This final WACAP Research Plan will be published as an EPA Report and will be available to interested parties via a website. The research plan is organized according to disciplinary (matrix) areas. After the introduction that discusses the rationale and general dimensions of the proposed work, each of the matrices to be sampled is discussed in considerable detail in separate, following sections. We view our approach as one that is interdisciplinary, integrated, and organized to develop an understanding of the problem we are addressing at multiple scales of time and space. We have explained in the individual sections how data from various components of the program will be used to assist in interpreting results across the program. One of the primary criteria for an integrated program is to conduct work in the same locations under a common objective. The WACAP program, as described in this research plan, is designed to meet this criterion.