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 10(2) to 5.5 x 10(7) cfu/g, and Fusarium moniliforme and Aspergillus species belonging to section Flavi were detected in 41 and 33 samples, respectively. Regarding the samples from the State of Paraná, F. moniliforme was present in 33 samples at a count of 1.0 x 10(2) to 1.6 x 10(7) cfu/g and Aspergillus spp. in section Flavi in 27 samples at 1.0 x 10(2) to 1.0 x 10(6) cfu/g. HPLC analysis of fumonisins in the corn showed that fumonisins B1 (FB1) and 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 FB1 levels of 4.79 micrograms/g and average FB2 levels of 3.95 micrograms/g: the Central-West region had average levels of 3.30 and 2.52 micrograms/g, and the Central-East had average of 3.25 and 2.34 micrograms/g, respectively. Except for one negative sample all the corn samples from the Central Region were positive for fumonisins, averaging FB1 levels being 5.45 micrograms/g and FB2 levels being 5.09 micrograms/g. Out of eight samples from the tropical state of Mato Grosso do Sul, F. moniliforme was detected in seven and Aspergillus spp. in section Flavi in five samples with average FB1 levels of 10.59 micrograms/g and average for FB2 levels of 10.31 micrograms/g. The samples from Goias were also contaminated with these two fungi, with the FB1 contamination being 5.83 and the FB2 contamination 3.62 micrograms/g.