Technical Abstract: Understanding the source of Aspergillus flavus is required to effectively manage within-field aflatoxin contamination of maize (Zea mays L.). Studies assessed the density of A. flavus propagules and other soil microflora (Fusarium spp., total fungi) associated with Mississippi Delta soils, and correlated soil factors with these populations. Soils from 12 and 15 sites were collected in 2000 and 2001, respectively. Propagule density of A. flavus ranged from log (10) 1.97 to 4.31 colony forming units (cfu) g-1 soil, while total fusaria ranged from log (10) 2.99 to 5.37 cfu g-1 soil. The highest populations of A. flavus were associated with soils containing higher organic matter, especially in sites under no-tillage management. The frequency of aflatoxin production in isolates ranged from 13 to 81% depending on soil. In 2001, there was a highly significant correlation between Aspergillus propagules and history of maize cultivation. However, in 2000, this was not observed. Overall soil fertility factors such as organic matter content, nitrate and extractable phosphorus correlated with the density of Aspergillus as well as Fusarium spp., and total fungi, but little relationship was observed with soil texture. The relationship between soil parameters and Aspergillus populations may be useful in predicting the contribution of soil microflora to aflatoxin contamination.