Information on breeding and wintering Harlequin Ducks (Histrionicus histrionicus) in Greenland is very limited, and no firm estimates of breeding and wintering numbers are available. However, it is assumed that only a few thousand pairs breed in Greenland. Numbers of molting males are estimated at 5,000 to 10,000 birds. They comprise both Greenland and eastern Canadian breeders; their proportions are unknown, but the latter may very well constitute a significant part. If true, Greenland has a significant responsibility for the well being of the eastern Canadian breeding population. Presently, there are no immediate threats to the Harlequin Duck population in Greenland. Hunting (illegal) has only negligible effects and habitat destruction is extremely limited. However, oil spills from transport of oil and increased offshore oil exploration constitute a potentially serious threat to molting and wintering birds from the breeding populations in Greenland and in eastern Canada.