Periodic disease is the prototype of a group of hereditary disorders characterised by recurrent inflammatory attacks. Since the discovery of the causing gene (MEFV) in 1997, three hospital laboratories in France, and around 20 throughout the world, propose a specific genetic test, based on the search of the common MEFV mutations on DNA extracted from a simple blood sample. This strategy allows definitive confirmation of periodic disease if one mutation is detected on each of the two chromosomes (around 30 mutations are reported today), but do not exclude the diagnosis in the other cases (one or no mutation detected). A non-contributive test shows the existence of rare MEFV mutations, or the involvement of another gene responsible for inflammatory hereditary syndrome; important differential diagnosis to be done, because their mode of management may be different from that of periodic disease.