The use of a rigorous and consistent indexing language is essential if a bibliography (whether manual or computerised) is to be used effectively; the adoption of a common language and indexing policy is a necessary prerequisite of co-operation and pooling of data between bibliographies. BHA, the successor to RILA and the Répertoire d’art et d’archéologie, has sought to develop and to apply such a language and policy in the environment of a bilingual database and publication, using English and French as befits a joint Franco-American project.