Adult sockeye salmon (Oncorhynchus nerka) were exposed to air supersaturated water in the laboratory from July 8 to August 13, 1974, approximately the same time period that they are exposed to supersaturated water during their movement through the lower and middle sections of the Columbia River. The first mortality occurred after 77h exposure at 120% saturation; 40% of the fish were dead after 127h. At 115% saturation the first mortality occurred after 523h (21 days) and 40% were dead after 835h (35 days). No further mortality occurred at 120 or 115%. However, at 120 and 115% saturation, survivors exhibited many sublethal lesions such as hemorrhaging and emphysema (bubbles) in the mouth, on the gills arches, body surface, and fins, etc. No deaths or signs of gas bubble disease occurred in the fish held at 110% saturation in water 2 ft (60 cm) deep. The lethal threshold was near 114% saturation.