A 2-year study was carried out to determine the efficacy of a biopesticide in reducing aflatoxin contamination in corn. The biopesticide, afla-guard, delivers a nontoxigenic strain of Aspergillus flavus to the field where it competes with naturally occurring toxigenic strains of the fungus. Afla-guard was applied to entire fields in two areas of Texas at either 11.2 or 22.4 kg/ha. Specific nontreated fields in close proximity to treated fields were designated as controls. Samples of corn were collected at harvest and analyzed for aflatoxins and density of toxigenic and nontoxigenic isolates of A. flavus. Aflatoxin concentrations were generally quite low in 2007, but the mean concentration in treated samples (0.5 ppb) was reduced by 85% compared with controls (3.4 ppb). In 2008, samples from treated and control fields averaged 1.5 and 12.4 ppb, respectively, an 88% reduction. There were no significant differences between the two afla-guard application rates. In conjunction with the reductions in aflatoxin contamination, treatments produced significant reductions in the incidence of toxigenic isolates of A. flavus in corn.