The 4 species of eider ducks, representing 3 genera, have circumboreal distribution. During the warmer months they occur as migrants or breeding birds in arctic Alaska, and great numbers of the 2 more common species are killed by the Eskimo for food. This survey was undertaken to determine the identity of cestodes obtained from eider ducks collected in Alaska during the past 5 years. The 4 species of ducks are: Steller's eider, Polysticta stelleri (Pallas); Pacific eider, Somateria mollissima v-nigra (Gray); king eider, Somateria spectabilis (L.); and spectacled eider, Arctonetta fischeri (Brandt). In addition to the birds taken by the writer, this report includes those collected by Dr. Robert Rausch, of this laboratory. A list of the cestodes identified and data on prevalence, host numbers, and collection localities are given. The literature contains reports of a number of cestodes from some of the eider ducks; however, many of the early descriptions are so incomplete that recognition of the species is difficult or uncertain. Relatively few of these species have been recorded subsequent to their original descriptions. Insofar as the writer has been able to determine, there are no previous records of cestodes from Steller?s eider. The present study has yielded additional information on the morphological characters of some of these poorly known species. On the basis of the Alaskan material, 2 species are redescribed herein and 2 previously unknown species are described as new.