Technical Abstract: Aflatoxin contamination of crops is a potential health hazard and a major economic problem in U. S. agriculture. Contamination results from the growth of the fungi, Aspergillus flavus and A. paraciticus, which invade certain crops in the field during periods of prolonged drought stress. Cyclopiazonic acid (CPA) is another potent mycotoxin produced by A. flavus that has been found as a contaminent of peanuts and corn. Prevention of mycotoxin contamination of peanuts and other commodities is the objective of a major research emphasis at this time. This paper reviews several years of studies that have shown that inoculation of soil with nontoxigenic strains of A. flavus and A. paraciticus yielded reductions of aflatoxin ranging from 30-90%. Results varied depending on the effectiveness of various nontoxigenic strains tested. Use of two specific nontoxigenic strains in a 1997 field study produced an average reduciton in CPA contamination of 85.7%. Thus, biological control appears to be an effective strategy for reducing preharvest contamination of crops with mycotoxins such as aflatoxin and CPA.