A biometric authentication method if provided for an individual to be authenticated amongst a very large quantity of individuals with an authentication system storing a set of reference information each associated to one of the individuals. The reference information is distributed across a plurality of sub-databases. The method includes a phase of adding reference information representative of a new individual, including selecting the sub-database that is best adapted to store the reference information to be added. A phase of authentication includes: provision by the individual of authentication biometric information and of an identifier forming addressing information, designating at least one of said sub-databases likely to contain the reference information representative of said individual; and searching amongst the reference information stored by the authentication system, of reference information corresponding to the individual, the searching being carried out on a subset of said set of reference information, identified by the addressing information.