Chuzan virus at 2 to 3 passage levels in cell cultures after isolation was inoculated intravenously into 15 seronegative pregnant cows at 89 to 150 days of gestation. All of the cows developed viremia a few days after inoculation and antibodies 2 weeks after inoculation. No clinical signs, except leukopenia, were observed throughout the experimental period. These 15 cows delivered 15 calves after normal gestation. One of the calves which was born to a dam inoculated at 120 days of gestation, showed impairment of movement, and the remaining 14 were healthy. Postmortem examination revealed that this calf had hydranencephaly-cerebellar hypoplasia (HCH) syndrome and that the remaining calves were normal. Two of the 15 calves, including the one that had HCH syndrome, had antibody to Chuzan virus in their precolostral sera. These findings provide additional evidence that Chuzan virus is the etiological agent of an epizootic of congenital abnormalities with HCH syndrome of calves in Japan, 1985 to 1986. We propose to name the HCH syndrome caused by Chuzan virus infection Chuzan disease.