SUMMARY.A total of 1037 birds, belonging to 17 species of Fringillidae (order Passeres) and nearly all collected in or near Syracuse, N. Y., were examined for blood parasites. Of the species of avian malaria,Plasmodium cathemeriumoccurred most frequently, followed byP. hexamerium, P. relictum, P. elongatum, andP. circumflexum.Other species were not seen, although some (e.g.P. nucleophilum, P. polare, P. vaughani) are known to occur in Central New York.A number of song, chipping, and field sparrows were given experimental inoculations ofPlasmodium vaughani‐infected blood and liberated. A few were recaught at varying intervals, but none were infected, suggesting that these species are insusceptible to this type of avian malaria.Malaria in song sparrows, which were caught in large numbers, is common and probably endemic, not varying greatly in frequency from year to year. But the incidence shows a sharp peak in the spring, most cases apparently being low‐grade relapses, which probably serve to reestablish the infection in the new crop of mosquitoes. There are indications thatHaemoproteusandLeucocytozoonbehave similarly.Infection with these last two parasites occurred in most of the species examined, but the incidence varied greatly, being especially high in white‐throated and white‐crowned sparrows. Reproductive stages ofHaemoproteuswere observed in the lungs of song and chipping s