Seven species of trypanosomes are known, of which Trypanosoma binneyi from Ornithorhynchus anatinus, T. thylacis from Thylacis obesulus, and T. hipposideri from Hipposideros bicolor albanensis are new. These are the first trypanosomes to be described from a monotreme, a marsupial, and an insectivorous bat in Australia. Six species of haemogregarines are known, of which Hepatozoon dasyuroides from Dasyuroides byrnei and H. pseudocheiri from Pseudocheirus laniginosus are new. One species of Hepatocystis is known from flying foxes, and one species of Polychromophilus from insectivorous bats. Four species of Babesia are known, of which B. thylacis from Thylacis obesulus is new. Four species of Theileria are known, of which Th. ornithorhynchi from Ornithorhynchus anatinus and Th. peramelis from bandicoots are new. The ox is the only domestic mammal harbouring sporozoan blood protozoa, three species being known, of which two are certainly pathogenic. Blood parasites, which appear to be related to bacteria or viruses, occur in cattle, rodents, and bandicoots. These include species of Anaplasma, Haemobartonella, and Eperythrozoon. Spirochaetes belonging to the genus Borrelia occur in the blood of cattle, rodents, kangaroos, and bandicoots.