The intracellular hematozoa of vertebrates are apicomplexan parasites with a life cycle consisting of 3 major phases: schizogony (asexual), gametogony (sexual), and sporogony (asexual). Most members have heteroxenous life cycles, wherein gametogony and sporogony occur in an arthropod vector and schizogony occurs in the vertebrate host. Leucocytozoon toddi occurs in Falconiformes and Leucocytozoon ziemanni in Strigiformes. Considered nonpathogenic in adult raptors, Leucocytozoon can cause mortality in nestlings. Haemoproteus is generally considered nonpathogenic in raptors; however, there are recent reports of fatalities in owls. Plasmodium is the true malarial parasite of birds and mammals. One species, Plasmodium relictum, is considered pathogenic for raptors. Atoxoplasma (previously Lankesterella) is an avian coccidian with both blood and intestinal stages. Babesia has been reported in raptors and might cause anemia and blindness in young falcons. In this article, advances in hematozoon diagnosis, treatment, and prevention are discussed. Although some hematozoa of raptors are considered nonpathogenic, high parasitemias in peripheral blood could indicate an underlying disease process.