When the HH1 strain of equid herpesvirus 1 was intranasally inoculated to mice, the virus propagated in mouse lungs and the animals showed clinical signs such as ruffled fur, hunched posture, depression and body weight loss. Mice recovered from these signs by day 12 and cleared the virus from their lungs and produced antibody by 7th day after infection. These convalescent mice did not allow growth of the rechallenged virus. Athymic nude mice, however, failed to clear the virus from their lungs. Most of field isolates from aborted fetuses were propagated in murine lungs but attenuated strains originated from the HH1 were not.