Research has been undertaken to develop a system, utilising highly efficient baculovirus vectors, for making foot and mouth disease (FMD) virus procapsids as the basis of a safe and effective vaccine. Four discrete antibody binding regions on FMD virus were identified. A complementary deoxyribonucleic acid (cDNA) clone of the type C procapsid was prepared. The functions of the 3 virus protease genes were studied by constructing cassettes of serotype O or A procapsid genes with various combinations of protease genes, and expressing them in a cell free translation system or in mammalian cells. Several were also made into baculovirus vectors, including one carrying all 3 protease genes. The latter, when used to infect insect cells, yielded small amounts of FMD virus protein able to self process to procapsid subunits, some of which then assembled into procapsid like structures. Difficulties encountered in trying to increase expression were traced to the toxic L protease, a problem that could be overcome by making deletions in the L gene. A new type of baculovirus vector, identifiable by a simple colour test and able to infect insect larvae, was developed.