Allozymic variation at 20 gene loci was estimated for populations of the Laysan Duck (Anas laysanensis) and the Hawaiian Duck (A. wyvilliana) from the Hawaiian archipelago, as well as for Mallard populations (A. platyrhynchos) from Hawaii and North America. The Laysan Duck and Hawaiian Duck are endemic, have experienced severe bottlenecks, and are listed as endangered species. Alternative alleles are fixed at six loci for Mallards versus Hawaiian anatids (Hawaiian and Laysan ducks). In contrast, every allelic variant found in the Laysan Duck was present in the Hawaiian Duck (but not vice versa), suggesting the former is an offshoot of the latter. The genetic distance (Nei's D) between Laysan and Hawaiian ducks is less than 0.01, while that between both Hawaiian and Laysan ducks and Mallards is greater than 0.45. The allozymic evidence also suggests that there has been extensive hybridization between Mallards and Hawaiian Ducks on Oahu, with the near disappearance of Hawaiian Duck alleles. However, there is only slight evidence of Mallard genic introgression into the Hawaiian Duck population on Kauai. Finally, the allozymic data suggest that the Hawaiian Duck is a distinct species from the Mallard, but that little genetic divergence has occurred between Hawaiian and Laysan ducks.