The antibacterial activity of arginine butyrate was tested on 15 different strains. Its bacteriostatic action was detected, depending on the organisms, at concentrations between 55 and 250 mM, except for the Streptococcus B. The latter was not only resistant, but its growth was even stimulated at low concentrations (1.95 mM to 31.2 mM). It is possible that this characteristic is related to its persistence in the female genital tract where the anaerobes produce butyrate. It has previously been demonstrated that this cytostatic activity applies not only to the prokaryotes, but also to the eukaryotes, where it is seen in much lower concentrations (6 mM): since the arginine butyrate could be used in antitumor treatment, it is important to investigate its bacterial growth effects.