The biology and distribution of arrowtooth, Atheresthes stomias, and Kamchatka, A. evermanni, flounder were examined in Alaskan waters to determine whether there were sufficient differences to justify treating them as separate species in resource assessment surveys conducted by the National Marine Fisheries Service. Geographic ranges of the two flounder species overlap in Alaska waters; both ... [Show full abstract] occur in the eastern Bering Sea and western Aleutian Islands region. However, only arrowtooth flounder occur throughout the eastern Aleutian Islands region and the Gulf of Alaska. Arrowtooth flounder were abundant over a wide range of depths (76-450 m) and were more abundant than Kamchatka flounder in catches shallower than 325 m. Kamchatka flounder were abundant only in deep trawl hauls (226-500 m) and were more abundant than arrowtooth flounder in catches at depths greater than 375 m. Arrowtooth flounder were also abundant over a wide range of bottom-water temperatures (2.1°-4.6°C), whereas Kamchatka flounder were abundant in a much narrower range of bottom temperatures (3.8°-4.2°C). By percentage, females dominated the arrowtooth flounder population in the eastern Bering Sea (68.6%) and Aleutian Islands region (59.6%), whereas the Kamchatka flounder population was 55.9% and 47.5% female, respectively. The females of both species attained greater length at age than did the males. The difference in growth between the sexes was greater among arrowtooth flounder and may account for the preponderance of females in the arrowtooth flounder population.