Cultures of Pseudomonas aeruginosa were tested for the production of bacteriocin-like substances, and differentiated with respect to three various indicator cultures. A technique was elaborated for the isolation of bacteriocin-like substances from a solid medium. Physico-chemical properties of Ps. aeruginosa were studied for the strains 8-H-3, PAO-406, and PAT-2. The molecular weight of bacteriocin-like substances was calculated for the strain 8-H-3.