Bacteriocins are proteinaceous antibacterial compounds that exhibit bactericidal activity against species closely related to the producer strain. The aim of this research was to investigate the production of bacteriocin by Bacillus spp. isolated from intestinal bacterial flora of the Caspian Frisian Roach (Rutilus frisii kutum). A bacteriocin produced by the bacterium Bacillus cereus strain RF 140 was identified. The antimicrobial activity started at the exponential growth phase and maximum activity was at the stationary growth phase. A crude bacteriocin obtained from culture supernatant fluid was inhibitory to indicator strains, including Listeria monocytogenes, Clostridium perfringens, and several species of Bacillus. Bacteriocin was stable at 80oC, but the activity decreased and was lost when the temperature reached 100 and 121oC, respectively. It was resistant to the proteolytic action of papain, catalase and amylase, but sensitive to proteinase K, pronase E and trypsin. Maximum bacteriocin activity was observed in the pH 4-9. This study indicates the importance of the bacteriocin produced by B. cereus strain RF 140 against food-borne pathogenic microorganisms such as L. monocytogenes and C. perfringens, and presents a potential for use as a biopreservative in food.