Sporocysts containing four sporozoites and measuring (avg.) 15.2 micrometers X 10.7 micrometers (N = 195) were shed in the feces of dogs (Canis familiaris) 8 to 16 days (avg. 11.6 days) after the first feeding of venison infected with Sarcocystis sp. Sporocysts containing four sporozoites and measuring (avg.) 11.5 micrometers X 8.1 micrometers (N = 35) were shed by a cat (Felis catus) 14 days after ingesting Sarcocystis-infected venison. Statistical (pooled t-test) comparison of the mean measurements of the sporocysts passed by the dog and cat demonstrated a significant difference (P less than .01). The raccoon (Procyon lotor) and opossum (Didelphis virginiana) could not be infected with Sarcocystis from white-tailed deer (Odocoileus virginianus). The name, Sarcocystis odocoileocanis, is proposed for the species transmitted from white-tailed deer to dogs. Sarcocystis odocoileocanis is differentiated from S. hemionilatrantis Hudkins and Kistner, 1977 of mule deer (Odocoileus hemionus), S. ovicanis Heydorn, Gestrich, Mehlhorn and Rommel, 1975 of sheep (Ovis aries) and S. cruzi Hasselmann, 1926 (=S. bovicanis Heydorn, Gestrich, Mehlhorn and Rommel, 1975) of cattle (Bos taurus) because S. odocoileocanis has (1) low infectivity for calves and sheep and (2) apparent insignificant pathogenicity for its intermediate host.