The content of empirically selected bacteriophage mixtures, produced by Microgen for the prevention and treatment of staphylococcal and pseudomonade infections, was investigated by negative stain electron microscopy. The main population of phages was shown to belong to the groups suitable for therapeutic purposes based on bioinformatics analysis of known genomes of Pseudomonas and Staphylococcus phages. However, the phage morphology studies did not always reveal the exact correspondence of the phage to the exact group. Therefore, we suggest group genotyping of the therapeutic bacteriophages on thebasis of genetic conservative locus.