A survey was carried out from 1983 to 1994 to determine the natural occurrence of aflatoxins and zearalenone in maize samples from Buenos Aires and Santa Fe provinces, Argentina. Among 2271 samples analysed, 1214 (53.5%) were contaminated with mycotoxins. Aflatoxin B1was identified in 445 samples (19.6%), aflatoxin B2was identified in 92 samples (4.1%) and zearalenone was identified in 676 samples (29.8%). Aflatoxin G1was detected in only one sample and none of the samples contained detectable amounts of aflatoxin G2. Aflatoxin contamination was not detected in the 1988, 1993 and 1994 harvests and, in the other years, with the exception of 1989, the contamination levels were low. Zearalenone was found every year.