The Foundational vs. Community Specific Services (CSS) Crosswalk and Guide supports health departments and health department systems as they seek shared understanding and agreement around the distinction between foundational activities and CSS in their jurisdictions. It includes general guidance for differentiating between Foundational Capabilities, Foundational Areas, and CSS, a list of common CSS by Foundational Area, and a crosswalk template for documenting program activities as foundational or CSS. These distinctions are particularly important for health departments and health department systems completing the FPHS Capacity and Cost Assessment to ensure costs and capacity are not being overestimated or gaps underestimated relative to foundational activities.