The Brazil nut tree (Bertholletia excelsa Humb. and Bonpl.) is indigenous to the Amazon rainforest. The nuts are collected as windfalls from wild growing trees during the rainy season. Brazil nuts are known to get infected with aflatoxin producing moulds leading to aflatoxin contamination of the nuts. The present study aimed at understanding the growth of aflatoxigenic moulds and aflatoxin production in Brazil nuts in relation to humidity conditions and storage time to support technical recommendations of good practices for preventing and controlling toxin formation. The results are divided into 3 parts: - Laboratory storage study: aflatoxin production and fungal growth in relation to storage humidity and time, correlation between mould and toxin levels; - Comparing the results from the storage study with field data; and - Laboratory study of the growth and aflatoxin production of different strains of aflatoxigenic fungi isolated from Brazil nuts: effects of strain variation, temperature and inoculum size. The conclusions were that the models can be used to evaluate the effect of storage humidity on the risk of high aflatoxin levels, to predict aflatoxin levels based on mould levels and to estimate how fast the risk of high aflatoxin levels increases under field conditions. The results from using different strains also indicate that the findings in the laboratory storage study generally are robust. The practical use of these models is already in force by indicating the maximum time at different points in the production chain and including those in guidelines for good practice. The present work was carried out within the framework of the Safenut project (http://stdfsafenutproject.com/) financed by the Standards and Trade Development Facility (STDF 114 -http://www.standardsfacility.org/) (Texte intégral)