The purpose of this paper is to present a preliminary evaluation of plankton data collected in the Pacific Northwest Region and to make recommendations regarding the advisability of continuing this data collection for pollution surveillance purposes. Under the proper conditions, plankton data can be a useful parameter in itself; however, its present role is to lend support to chemical and physical data. These plankton data have provided almost ten years of 'badeline' data at certain points in the Northwest Region. At a later date, if needed, these data could prove to be of historic value if and when a comparison needed to be made between two periods of time to determine water quality changes.