In order to determine the impairment of water quality and assess the effects of contaminants on the biota, field surveys of selected areas of the boundary waters in Ontario were undertaken by the Canadian Task D, Subactivity-3 of the International Joint Commission, Pollution from Land Use Activities Reference Group (Lower Great Lakes). The primary purpose of this study was to determine the levels of persistent contaminants in the biota of estuaries of the drainage basins chosen, as well as to interpret the results in terms of biological significance by utilizing the available information in literature.