The present study was undertaken to evaluate the effect of gamma irradiation on two heat-resistant moulds, namely Aspergillus fumigatus and Paecilomyces variotii isolated from margarine samples. The irradiation process of these moulds was carried out in a Co-60 gamma (gamma) irradiator at average absorbed doses of 1, 3, 5 and 7 kGy for exposure times of 52, 156, 260 and 364 min, respectively. The average D-10 value for A. fitmigatus was 1.08 +/- 0.08kGy while it was 0.59 +/- 0.10kGy for P. variotii. Consequently, the sensitivity of P. variotii against gamma irradiation was more than A. fumigatus. (c) 2007 Elsevier Ltd. All rights reserved.