Development of an in vitro culture system for infectious Dictyocaulus viviparus larvae made it possible to study the potential cross-transmission of D. viviparus between white-tailed deer (Odocoileus virginianus) and cattle (Bos taurus). Between 26 September 1995–29 February 1996, six parasite-free bull calves were individually inoculated with 15 to 50 infective third stage larvae (L₃)/kg of body weight cultured from adult D. viviparus collected from white-tailed deer. Three bull calves were simultaneously inoculated with 45 L₃/kg of body weight recovered from cattle either by the Baermann technique or by in vitro culture as above. All three calves inoculated with the homologous cattle strain became patently infected while all six calves inoculated with the heterologous deer strain remained negative for the presence of D. viviparus in the feces and in the lungs upon necropsy.