Epontic and benthic amphipods (Onisimus litoralis, Onisimus juveniles, Gammarus setosus, Anonyx nugax, and A. makarovi) and a pelagic mysid (Mysis oculatus) were collected under ice at Little Cornwallis Island, Northwest Territories, Canada. They were exposed, on site, to dissolved zinc and lead to determine lethal concentrations (LC50s). Incidental information was obtained on salinity and temperature tolerance. Subsequent testing of a temperate amphipod and oyster larvae exposed to the two metals provided comparative data to augment a literature review. The Arctic invertebrates were surprisingly insensitive under all test conditions. The implications for Arctic developments, particularly those involving near-shore, point-source discharges, are discussed and recommendations are made for effectively expanding a presently depauperate Arctic marine toxicity database.