Of 150 fecal samples from coyotes from northern Utah and southern Idaho, 21 contained coccidian sporocysts. These were found singly, contained four sporozoites and a granular residuum, and averaged 16.9 x 10.9 mum in size. None of four lambs inoculated with these sporocysts showed clinical signs of disease, and no parasites were found in their tissues. One calf inoculated with 135,000 sporocysts and another inoculated with 720,000 sporocysts eventually became unable to rise from recumbency. One was killed after 43 days; the other died at 50 days. Both calves had a mild mononuclear cell infiltration into the connective tissue adjacent to vessels in the heart, other striated muscles, kidney, and liver, and a moderate lymphoid hyperplasia in the spleen and lymph nodes. Schizonts were observed in a lymph node, and young sarcocysts were observed in skeletal and cardiac muscles. Four coyotes fed bovine heart infected with Sarcocystis passed sporulated sporocysts in their feces that were indistinguishable from those in the fecal samples from Utah and Idaho.