Renal coccidiosis was found in 4 of 12 oldsquaw ducks (Clangula hyemalis) collected from the north slope of Alaska and Prince William Sound. Numerous 1 to 2 mm white foci were observed on the kidney surface of one bird. Microscopically, there was distention of renal tubules with oocysts, flattening of tubular epithelium, and interstitial accumulation of mononuclear cells. Kidneys from several other species of sea ducks from Prince William Sound were not infected.