A total of 213 wood ducks (Aix sponsa) from 24 localities in 12 states in the Atlantic Flyway was examined for blood parasites in 1976 and 1977. Hematozoa were present in birds from every collection site from Virginia northward to Maine. Only one infection was detected in birds from North Carolina southward to Florida. Haemoproteus nettionis was the most common parasite, occurring in 56% of the northern wood ducks; Leucocytozoon simondi (20%), Plasmodium circumflexum (6%), and microfilariae (18%) were found also. Plasmodium, Leucocytozoon, and microfilariae were more commonly observed in juvenile birds than adults. There was no difference in prevalence between male and female ducks. The prevalence of each parasite species varied among collection sites in the northern states.