Bovine viral diarrhoea virus (BVDV) is a pestivirus with worldwide distribution. Infections are common in New Zealand with an estimated 85% of herds infected. BVDV infection leads to a range of disease problems but reproductive failure is the principal cause of economic loss. The following trial was undertaken to determine if vaccination of sero-negative heifers with a multivalent viral vaccine containing a 1a BVD strain (NADL) was able to protect the foetus from infection with a field strain of BVDV.