Foot-and-mouth disease virus (FMDV) exists as multiple serotypes and strains that infect a range of cloven-hoofed animals with variable severity. Clinical diagnosis reinforced by diagnostic tests support timely intervention, whilst virus characterisation helps trace routes of spread and select appropriate vaccine strains. To speed up and simplify diagnosis, penside tests have recently been developed. Serology is used to identify undisclosed infection and substantiate freedom from infection and specific tests are needed to detect infected animals in vaccinated populations. Serology is also used to estimate post-vaccinal population immunity. Contingency plans are required to enable countries to scale up diagnosis at short notice. Improvements are needed in preclinical and penside diagnosis and in our ability to model vaccine effectiveness.