We examined the winter diet of Steller's Eiders (Polysticta stelleri) in Varangerfjord, northern Norway, by analyzing the esophagus content of 29 individuals (12 juveniles and 17 adults). A total of 8389 prey items of 31 species were identified: 13 species of gastropods (making up 68.4% of total number of items); 4 species of bivalves (18.5%); 12 species of crustaceans (13%); and 2 species of echinoderms (<0.1%). In terms of percentage aggregate wet weight 31.4% was gastropods, 22.6% was bivalves, and 41.4% was crustaceans. Juvenile eiders ate more crustaceans (x̄ = 61% aggregate w.w.) than adults (x̄ = 26%, P < 0.05), possibly because they were in poor body condition and may have had higher energy requirements than adults. Adults tended to eat more gastropods (x̄ = 41% vs 22%) and Mytilus edulis (x̄ = 27% vs 12%) than juveniles. There were only small differences between sexes. Most of the prey items were of species known to be associated with kelp plants, especially Laminaria hyperborea, suggesting that Steller's Eiders obtain a large proportion of their prey directly from the vegetation.