Blood films from 60 mallard (Anas platyrhynchos) and 67 pintail (A. acuta) ducks, collected in Alberta and the Mackenzie Delta, Northwest Territories, during 1973 and 1974, were examined for blood parasites. Twenty-two (37%) of the mallards and fourteen (21%) of the pintails were infected with one or more species of hematozoa. Infections of Leucocytozoon simondi occurred more frequently (86%) than Haemoproteus nettionis (22%) in the infected birds. Trypanosoma avium occurred in one individual of each species of duck; one pintail harbored an unidentified microfilaria. Differences of prevalence between species are predicted on the basis of host attractancy to vectors and/or host habitat selection, and are discussed.