Aflatoxin B1 is known as the most potent mycotoxin produced by several fungi. It has been demonstrated to be not only carcinogenic but teratogenic and mutagenic as well in humans. To prevent or inactivate aflatoxins, several chemical of physical methods were tested for ammoniation, using insecticides as an wxample, but they were unsuitable for food products. On the contrary, biological control by antagonistic microorgani는 is and ideal method. In order to control aflatoxin B1 biologically, the antagonists #07, #63, #75, #74, and #61 were separated from various samples by using the antagonistic activity test. Among them, culture filtrate part A (non heat-treated) of #63 and #74 on aflatoxin B1 produced by Aspergillus fkavus were shown to be 95% and 75%, respectively. Based on the morphological characteristics, #63 was deduced as an Azospirillum sp.