We had shown in preliminary studies with a small number of animals that antibodies against 2C could be detected in cattle and pigs which had been infected with FMDV but not in animals which had been vaccinated against the disease. To determine whether this test was generally applicable, seta from several hundred animals which had been vaccinated with different products in many countries have been tested in an ELISA using baculovirus expressed 2C. Our results show that only 1–2% of the sera gave a positive reaction by this method. In contrast, 100% of sera from convalescent animals gave a positive reaction.