Cotton is a crop grown for fiber and seed cotton, which is used as a feed additive for livestock. Therefore, any contaminant that jeopardizes the quality of cottonseed can result in both health and economic losses. Several Aspergillus fungi can contaminate cottonseed with the carcinogenic mycotoxins, aflatoxin (AF) and sterigmatocystin (ST). If cottonseed contains AF levels (more commonly analyzed than ST) above the accepted national and international limits, the seed must be destroyed or decontaminated. Our longterm goal is to eliminate the ST/AF problem by first understanding how ST/AF biosynthesis is regulated in Aspergillus and then applying this understanding in a logical control strategy.