This report examines the role that federal environmental regulations play in the context of the federal-state standard setting relationship. Chapter one provides an overview of how federal regulations relate to standard setting. Chapter two identifies the general policy consequences of allowing state program flexibility. Chapter three examines how federal regulations currently provide for flexibility in this relationship. Chapter four evaluates the techniques used by the federal government to afford or restrain flexibility. Chapter five provides a summary of the issues that must be addressed in constructing or reconstructing a federal regulatory regime that encourages or restrains State flexibility.