In order to evaluate whether cattle vaccinated with an inactivated vaccine against bovine viral diarrhoea virus (BVDV) can be differentiated serologically from BVDV infected animals, two different aspects were investigated. Firstly the antibody response against non-structural proteins (NS) was measured after multiple vaccinations of cattle with a single or double dose of a commercially available inactivated BVDV vaccine. In a second study, the animals were first vaccinated with the product, and then infected with BVDV. The antibody response was determined in four different commercial ELISA systems. It can be concluded, that the inactivated BVD vaccine exhibits properties of a marker vaccine when an appropriate antibody NS3 ELISA is applied: after vaccination NS3-specific antibody levels are low or undetectable, but the vaccination does in the present study not show any interference with the development of antibodies against NS3 after subsequent field virus infection.