A collection of 45 serologically distinct strains of Morganella morganii from several European countries was typed by morganocin production (p) and sensitivity (s). This permitted their differentiation into 33 morganocin p/s types; 15 new types of morganocin and one new morganocin sensitivity type were found and are defined. Morganocin production and sensitivity characteristics appeared to be unrelated to the O and H antigens of the strain. The finest strain recognition in M. morganii might be achieved by a combination of bacteriocin and serotyping methods.