Four commercially available ELISAs for detection of antigens associated with the bovine viral diarrhoea virus in persistently infected cattle have been compared. The tests are equally specific (100%) and the sensitivity of three ELISAs is comparable with that of a conventional cocultivation assay. Performing ELISA on samples from young animals that received colostrum may yield false negative results because of interference of maternal antibodies in the tests. It is concluded that ELISA can be a valuable tool in eradications programs when large numbers of cattle are to be monitored.