A representativeness assessment of National Forest System (NFS) Research Natural Areas in Idaho summarizes information on the status of the natural area network and priorities for identification of new Research Natural Areas. Natural distribution and abundance of plant associations is compared to the representation of plant associations within natural areas. Natural distribution and abundance is estimated using modeled potential natural vegetation, published classification and inventory data, and Heritage plant community element occurrence data. Minimum criteria are applied to select only viable, high quality plant association occurrences. In assigning natural area selection priorities, decision rules are applied to encompass consideration of the adequacy and viability of representation. Selected for analysis were 1,024 plant association occurrences within 214 natural areas (including 115 NFS Research Natural Areas). Of the 1,566 combinations of association within ecological sections, 28 percent require additional data for further analysis; 8, 40, and 12 percent, respectively, are ranked from high to low conservation priority; 13 percent are fully represented. Patterns in natural area needs vary between ecological section. The result provides an operational prioritization of Research Natural Area needs at landscape and subregional scales. Objective ranking criteria provide clear accounting of priority assignments that are easily updated to reflect changing information or conditions.