The apicomplexan protozoan genus Atoxoplasma Garnham, 1950 is resurrected and the family Atoxoplasmatidae n. fam. established for homoxenous blood parasites of birds that develop asexually in both the blood and intestinal cells, and form oocysts that are passed unsporulated in the feces, sporulate on the ground, and then infect new hosts. A list of 19 species of Atoxoplasma is given. Atoxoplasma desseri n. sp. of the evening grosbeak Coccothraustes vespertinus and rose-breasted grosbeak Pheucticus ludovicianus is named.