The U.S. Environmental Protection Agency (EPA) is conducting a review of the existing air quality criteria for particulate matter (PM) and the primary (health-based) and secondary (welfare-based) national ambient air quality standards (NAAQS) for PM. The purpose of this document is to communicate the plan for reviewing the air quality criteria for PM associated with human health and welfare effects and the primary and secondary standards for PM. This review will provide an integrative assessment of relevant scientific information on PM and will focus on the basic elements of the primary and secondary PM air quality standards: the indicator, averaging time, form, and level. These elements, which serve to define each ambient air quality standard, must be considered collectively in evaluating the health protection afforded by the standard. The current standards use PM2.5 and PM10 as the indicators for fine and coarse particles, respectively. This integrated review plan is organized into eight sections. Section 1 presents background information on the recently revised NAAQS review process, the legislative requirements for the review of the NAAQS, past reviews of the NAAQS for PM, and the scope of the current review. Section 2 presents the current review schedule. Section 3 presents a set of key policy-relevant questions that will serve to focus this review on the critical scientific and policy issues. Sections 4 through 8 discuss the planned scope and organization of the key assessment documents, the planned approaches for preparing the documents, specific monitoring issues, and plans for scientific and public review of the documents.