Muscle samples from 1497 Australian mammals, comprising 73 spp. (2 monotreme, 48 marsupial, 3 cetacean, 1 lagomorph, 10 rodent, 2 canid, 3 chiropteran and 4 cervid) were examined histologically for cysts of Sarcocystis. Cysts were recorded in 126 (8.4%) of the mammals examined. Type A cysts (cysts with thich walls and/or large zoites and/or internal trabeculation) were found in 77 (5.1%) of these mammals, representing 13 spp. (4 marsupial, 1 cetacean, 1 lagomorph and 7 rodent). Type B cysts (cysts with thin walls and small zoites) were found in 50 (3.3%) of the animals, representing 20 spp. (14 marsupial, 1 cetacean and 5 rodent). The greatest prevalence of type A cysts (21.1%) was found in rabbits, Oryctolagus cuniculus. Among the rodents examined, type A cysts were more frequently encountered (11.1%) than type B (2.2%). In 4 spp., Rattus fuscipes, R. rattus and Mus musculus, both types of cyst were found. Both types of cyst also were recorded in the macropodid marsupials, but type B cysts were encountered more frequently (7.2%) than type A cysts (1.7%) and only in 1 spp., Macropus rufus, were both forms detected. Type B cysts were found in macropods in Tasmania as well as on the mainland of Australia, whereas only the mainland marsupials harbored type A cysts. Scrapings of intestinal mucosa or feces were examined from 92 dasyurid marsupials, comprising 5 spp., and from 55 feral cats (Felis domesticus). Sporulated sporocysts typical of Sarcocystis or Frenkelia were found in 1 Tasmanian devil, Sarcophilus harrisii, 1 tiger cat, Dasyurus maculatus, and 1 feral cat.