Peanut (Arachis hypogoea) is an important crop in Mali, West Africa. One of the main problems with the peanut production is the detection of high levels of Aflatoxin B1. Thus, research is needed in order to improve the quality of peanut by reducing the contamination rate by Aspergillus flavus and Aflatoxin B1. The objectives of this work were 1) to determine the rate of progress of A. flavus and Aflatoxin B1 in granaries located in 26 villages and also in the granaries located in the corresponding 26 markets in Mali and 2) to correlate the progress of the A. flavus and Aflatoxin B1 with environmental variables outside the peanut granaries, in order to provide early prediction of high levels of Aflatoxin B1. During the period 1999/2000, 2000/2001 and 2001/2002 peanut samples were taken every two months from 26 granaries at villages and 26 granaries at the local markets. One kilogram of peanut was collected from the previously mixed stock and then submitted to a laboratory for determinations of A. flavus levels and Aflatoxin B1. The analyses of A. flavus in the 26 villages' granaries during the three years of the experiment showed that there were low counts of the fungus colonies for the month of February and a consistent increase from February to August, reaching a plateau from August to December. However, there was a high standard deviation during these months, indicating a significant variation between granaries of the individual villages. In general, the peanut were highly contaminated by A. flavus and the average rates of Aflatoxin B1 were significantly higher than the accepted international standards. Attempts are being made towards modeling the contamination risk of peanuts stocks by A. flavus and Aflatoxin B1 with climatic conditions, in order to develop an early warning system for Aflatoxin B1.