Twenty-one Branhamella catarrhalis strains selected for their diversity by esterase electrophoretic polymorphism, and belonging to 20 distinct zymotypes, were studied by restriction fragment length polymorphism (RFLP) of total DNA after ethidium bromide staining and of ribosomal DNA regions (ribotyping). The former analysis allowed the distinction of 20 patterns and the latter the delineation of 19 ribotypes. The three methods were correlated and showed a clonal diversity of the species. Esterase electrophoresis and Hinfl RFLP patterns after ethidium bromide staining appeared to be simple tools for use in B. catarrhalis epidemiology.