This study investigated the occurrence of aflatoxin B1 in peanuts and peanut products marketed in the State of Rio Grande do Sul, Brazil. One hundred one samples of peanuts and peanut products were collected and analyzed by thin-layer chromatography with a charge-coupled device system. Aflatoxin B1 was present in 14% of the samples analyzed, in concentrations ranging from 24.0 to 87.5 µg/kg in the peanut samples and from 22.0 to 84.6 µg/kg in the peanut-product samples. These values exceeded the Brazilian regulatory limit (20.0 µg/Kg for aflatoxins B1+G1+B2+G2 ). These results suggest that although aflatoxin contamination in peanuts marketed in southern Brazil is lower than in other Brazilian regions, it is still a serious problem for human health and the economy.