A previously undescribed Bacillus species has been characterized. The organism was isolated from a blood transfusion bottle implicated in a fatal bacteriogenic transfusion reaction and has been examined from a number of different aspects to characterize it as completely as necessary to provide identification. It was placed into group 3 of the genus Bacillus on the basis of its cellular morphology, the morphology of the sporangium, and the location of the spore within the cell. There are only three other species described in this group. Since the organism differed markedly from each of these, it appears to represent a new species.