The influence of the preparation of hemocytolysin, obtained from V. cholerae non O1 (strain P-11702), on the growth of V. cholerae cells was studied. The study revealed that hemocytolysin is capable of inducing partial or complete bacterial lysis on the place of its application, depending on the protein load of the substance and the inoculation dose of microbes. Two electrophoretic fractions with molecular weights of 14 and 14.5 kD induced the cytolysis of sheep, rabbit, guinea-pig red blood cells and showed a bactericidal effect. The different sensitivity of Vct+ and Vct- strains of V. cholerae to different doses of hemocytolysin was studied.