While engaged in research on members of the genus Eimeria infecting Wyoming sheep, an undescribed species was observed. The parasite was recovered from two of nine animals housed at the Wyoming State Veterinary Laboratory at Laramie, Wyoming. Both animals had multiple infections; oocysts of Eimeria airloingi, E. ah-sa-ta, E. parva, E. nina-kohl-yakimovi, and E. crandallis were recovered from both sheep and in addition E. faurei and E. intricata were present in one. Infections with the new species were relatively light, the largest number of oocysts observed being in the order of 20 per gram of feces. This peak in numbers of oocysts was present on only one day although the infection persisted over a period of eleven weeks.