Production losses and treatment expenditures consecutive to bovine viral diarrhoea virus (BVDV) infection in a dairy herd were calculated by partial budgeting based on published estimates of production effects. Overall costs (losses plus expenditures) resulted in a decreased gross margin of €10.7 and 19.0 per 1000 l of milk for an average and severe infection, respectively. With a milk quota system allowing no lease of quota, assuming adjustment of the herd size by the farmer to produce the quota, decrease in gross margin was limited to €7.9 and 13.9 per 1000 l of milk.