Two toxigenic molds, Aspergillus flavus Link and Penicillium rubrum Stoll, were isolated from corn implicated in an outbreak of moldy corn toxicosis,1 a disease first described in pigs and cattle.2 During the early stages of work on moldy corn toxicosis P. rubrum seemed to be the more toxic mold and it was not until a few years later that the importance of A. flavus and the aflatoxins became apparent. Although P. rubrum was first associated with the etiology of moldy corn toxicosis in farm animals it soon became evident that this disease had a complex etiology which may involve species of Penicillium, Aspergillus, and Fusarium.