Aflatoxins are toxic secondary metabolites produced by Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius. A regulatory gene, aflR, is involved in regulation of aflatoxin biosynthesis and the sequence has been published. In this study, rapid assessment of aflatoxigenic fungi in food was accomplished using an indigenously designed primer pair for the aflatoxin regulatory gene aflR in polymerase chain reaction (PCR). Specificity was assayed in pure and mixed culture systems using DNA extracted from 28 different fungal strains as PCR template. Positive amplification was achieved only with DNA from aflatoxigenic A. flavus and A. parasiticus. The detection limit for mycelium and spores was determined as 0.05 g and >= 100 cfu, respectively. Specificity and sensitivity of PCR assay in groundnuts and maize for A. flavus was possible with as few as 100 cfu/g. (c) 2005 Elsevier Ltd. All rights reserved.