Since animal intoxication related to corn‐based feed is frequently observed in the State of Paraná, Brazil, natural contamination by fumonisins in 48 corn samples (39 from the State of Paraná, and 9 from the Brazilian tropical states, Mato Grosso do Sul and Goias) harvested in 1990–1991 was investigated, along with fungal flora. The total mould count ranged from 6.3 X 102to 5·5 X 107cfu/g, andFusarium moniliformeandAspergillusspecies belonging to sectionFlaviwere detected in 41 and 33 samples, respectively. Regarding the samples from the State of Paraná,F. moniliformewas present in 33 samples at a count of 1.0 × 102to l.6X107cfu/g andAspergillusspp. in sectionFlaviin 27 samples at 1.0 X 102to 10 X 106cfu/g. HPLC analysis of fumonisins in the corn showed that fumonisins B1(FB1and B2(FB2) were positive for 97.4% and 94.8% of samples respectively. All the corn from North Paraná was positive for fumonisins, with average FB1levels of 4·79μg/g and average FB2levels of 3.95μg/g: the Central‐West region had average levels of 3.30 and 2.52μg/g, and the Central‐East had average levels of 3.25 and 2.34μg/g, respectively. Except for one negative sample all the corn samples from the Central Region were positive for fumonisins, averaging FB1levels being 5.45μg/g and FB2levels being 5.09μg/g. Out of eight samples from the tropical state of Mato Grosso do Sul,F. moniliformewas detected in seven andAspergillusspp. in sectionFlaviin five samples with average FB1levels of 10.59μg/g and average for FB2levels of 10.31 μg/g.The samples from Goias were also contaminated with these two fungi, with the FB1contamination being 5.83 and the FB2contamination 3.62μg/g.