Bulk dust samples obtained from grain elevators in the central Illinois area were analyzed for aflatoxin (AFT) content using instrumental two‐dimensional high performance thin‐layer chromatography (HP‐TLC). AFT B1levels ranged from nondetect‐able up to 3.5 ppb. This is the first report of AFT occurring in dust in northern grain mills. Long‐term exposures of workers to AFT contaminated dust via the respiratory route could pose some hazard.