Further studies on moose revealed trypanosomes in two captive moose (Alces alces shirasi) and in 4 of 7 free-ranging moose in Wyoming by blood culture. Two free-ranging moose from Utah were negative. One of two additional captive moose calves was positive for trypanosomes. Trypanosomes also were detected in blood cultures of 8 of 39 American bison (Bison bison) being brought into Wyoming from Nebraska. Nineteen additional bison were negative for trypanosomes by blood cultures. Identification of species was not possible due to the failure to obtain bloodstream trypomastigotes from this host. Trypanosomes were recovered from 8 of 57 pronghorn antelope (Antilocapra americana). This is the first report of Trypanosoma sp. from bison and from pronghorn; the trypanosome from moose was identified as Trypanosoma cervi from bloodstream trypomastigotes. In 1978, natural transplacental transmission of trypanosomes was found to occur in 1 of 15 mule deer (Odocoileus hemionus) fetuses, examined near term by blood culture. No trypanosomes were found in 18 mule deer fetuses examined in 1979. Of 100 free-ranging elk from western Wyoming examined by blood culture in 1979, 71 were infected. These data are compared with data from 1973-74.