A total of 1852 anatids of 14 species from various locales in Massachusetts were examined for hematozoa; 1064 (58%) of 10 species were found to harbour one or more blood parasites. Haemoproteus (P.) nettionis was the commonest parasite, occurring in 90% of the infected birds; Leucocytozoon simondi occurred in 27% while Plasmodium circumflexum occurred in 14.5% of the infected birds. Prevalence of parasitism was somewhat higher in adult than in immature birds and the rate of infection varied widely from area to area within the state but was fairly stable within any one region during each of the four years of the survey. Seasonal prevalence of the parasites indicated that transmission occurred twice each season suggesting at least two major vectors for each hematozoon.