In the present work the occurrence of aflatoxin in peanut (Arachis hypogaea L.) in the region of Fernandópolis, S.P., was investigated in three Stages, from harvest to industrialization: a) by the time the grower sells it to the oil mill: Epochs I and II; b) during its storage prior to milling: Epochs III and IV, and c) after oil extraction (peanut flour) : Epochs V and VI. In each Stage two collections, of 10 samples each, were made in a total of 40 samples of peanuts and 20 samples of peanut flour. From the results the following conclusions could be drawn: 1) all samples were toxic, except one; 2) the toxicity level in terms aflatoxin B1 was high, for 51.7% of the samples were in the category "High" and 38.3% in the category "Very High"; 3) the levels of aflatoxin in the samples grew from Epoch I to Epoch IV: mean values of 0.54 to 2.14 ppm, decreasing in Epoch V and VI: 1.04 ppm; 4) Five samples were excessively toxic with more than 10.00 ppm; 5) aflatoxin and high moisture content are present in most raw material when the grower takes it to the oil mill; 6) the miller does not take action to dry the moist material, contributing, this way, to permit an increase in the aflatoxin levels, during storage.