Eighteen phages were studied by electron microscopy. They belonged to eight morphotypes representing the Myoviridae, Siphoviridae and Podoviridae families of tailed phages. Twelve phages were members of known species and six phages belonged to three new species. Results correlated closely with serological and DNA-DNA hybridization data. Induced and non-induced propagating bacteria were investigated for lysogeny. All strains produced R-type pyocins, phage-like particles or inhibitory reactions. The identity of typing phages should be controlled periodically.