In an attempt to determine if pregnant mice could be protected from abortion subsequent to challenge with equine herpesvirus-1 (EHV-1) in the mouse model of EHV-1 disease, female BALB/c mice were inoculated with baculovirus-expressed EHV-1 glycoprotein B (bac-gB), wild-type baculovirus (bac-wt), rabbit kidney (RK-13) or baby hamster kidney (BHK-21) cells. Using an ELISA, antibodies against EHV-1 were detected in the serum of mice following two injections of bac-gB and were enhanced by a third injection, after which low levels of neutralising antibody were also detected. After mating, mice in the bac-gB, bac-wt and RK-immunised groups were infected intranasally with 10(7) pfu of EHV-1 on day 16 of pregnancy. All challenged mice experienced body weight loss post-infection (pi). However, postnatally, the gB-immunised group demonstrated body weight gain which was not seen in the other groups. There were no maternal deaths in the gB-immunised group but 1/6 bac-wt-immunised and 3/6 RK-immunised mice died post-challenge. Litter survival rate was significantly higher (p < 0.001) for the gB-immunised dams (54%) than that of either the bac-wt-(9%) or RK-immunised (0%) dams and the mean body weight of young from the surviving bac-wt-immunised litter was significantly (p = 0.021) lower than either the gB-immunised group or the BHK-immunised unchallenged group at 10 days of age. The virus was not isolated from any foetus from a gB-immunised dam. However, the virus was detected in 9% of foetuses from bac-wt-immunised and 21% of foetuses from RK-immunised dams.