The levels of aflatoxins and zearalenone were determined in 328 samples of corn from the States of Santa Catarina, Minas Gerais, São Paulo, Paraná, Rio Grande do Sul and Espirito Santo by thin‐layer chromatography; the samples were obtained from April 1985 through to March 1986. In 12·3% of these samples aflatoxin B1was detected in concentrations that varied from 10 to 900 ug/kg (ppb); 18 samples showed levels above those tolerated by Brazilian legislation. Zearalenone was found in 4.5% of the samples analysed in concentrations that varied from 653 to 9830 μg/kg (ppb). The limit of detection of the method for the determination of zearalenone was 260 μg/kg (ppb) and the recovery was 100%.