A total of 3.449 birds, representing 195 species of 33 families from three areas in São Paulo State, Brazil, were examined for hematozoa during the period 1967-1972. Only 268 birds (7.8%) of 21 families harbored a blood parasite, which represented by species of Haemoproteus (3.5%), microfilaria (2.6%), Plasmodium (1.8%), Trypanosoma (0.8%) and Leucocytozoon (0.06%). The prevalence was similar in each of the six years of the study but a marked decrease in prevalence was noted in February and June of each year. The prevalence of parasitism was significantly different in each of the three areas sampled.