One hundred samples of Brazil nuts from the States of Amazonas and São Paulo, were analysed mycologically and toxicologically for aflatoxins B1 and G1. Three hundred and twelve fungi were isolated of which 91 were of the genus Aspergillus, 83 of the genus Penicillium and the remainder included 23 different genera. Amongst the Aspergillus samples, 26 were producers of aflatoxin, distributed into three species: Aspergillus flavus Link (18); Aspergillus parasiticus Speare (7) and Aspergillus fresenii Subram (1). Of the 100 extracts of analysed nuts, three were afiatoxin-positive.