The work described in this report was initiated during the Interior Columbia Basin Ecosystem Management Project (ICBEMP). The ICBEMP produced a broad-scale scientific assessment of ecological, biophysical, social, and economic conditions for the interior Columbia River basin and portions of the Klamath and Great Basins. The broad-scale assessment made extensive use of potential vegetation (PV) information. This report (1) discusses certain concepts and terms as related to PV, (2) describes how a PV framework developed for the broad-scale ICBEMP assessment area was stepped down to the level of a single section in the national hierarchy of terrestrial ecological units, (3) describes how fine-scale potential vegetation types (PVTs) identified for the Blue Mountains section were aggregated into the midscale portion of the PV hierarchy, and (4) describes the PVT composition for each of the midscale hierarchical units