Research Natural Areas are examples of typical and distinctive natural ecosystems and habitats reserved for scientific and educational use. This outline of the minimal Research Natural Area system needed to provide adequate field laboratories for ecological, environmental, and land management research was developed by an interinstitutional, interdisciplinary working group. Natural area needs were first described on the basis of individual organisms, habitats, or ecosystems which should be represented. These "cells," the basic building blocks in defining the total scope of the system, considered terrestrial and aquatic environments as well as rare and endangered species. Identified cells were matched against existing Research Natural Areas to determine which were already filled. The remaining, unfilled cells were then tentatively grouped as units which were listed as Research Natural Area needs. A minimal Research Natural Area system for Oregon and Washington requires approximately 360 tracts which, in turn, incorporate over 770 individual cells (ecosystems, habitats, or organisms). Since 60 Research Natural Areas are already established, about 300 additional areas are needed. These remaining needs were assigned a priority (low, medium, or high) based on importance and degree to which they are endangered, as well as identified as to the Federal, State, or private agency or institution most likely to be able to provide a tract of that type. The purpose of Research Natural Areas, their place in land planning, history of Research Natural Area activities in the Pacific Northwest, and general observations and recommendations on unresolved problems are also outlined.