The most dominant fungi which were found to be associated with yellow grains could be arranged descendingly, according to the occurrence percentage, as follows : Aspergillus fatvus, Penicillium fimiculosum, Asp. terreus, F. moniliforme, F. oxysporum, F. graminearum, Asp. niger, Altemaria sp., Rizopus sp., Macrophomina phaseolina and Fusarium sp. The percentage of infection of yellow corn grains caused by A. flavus was significantly increased by increasing the storage temperature degree, grain moisture content, time of storage and percentage of broken Kernels (grade of the grains). The tested fungicide, Rovral 50% and Topsin M 70% were successively decreased the percentage of infection of yellow corn grains caused by A. flaws. Each fungicide at any tested rate significantly decreased grain invasion. The efficiency of each fungicide was significantly increased by increasing its concentration. The usage of both fungicides at the rate of 1000 ppm caused the least percentage of grain infection, specially after storage period of 15 days. The infection percentage was influenced by application of the tested preservatives, thiourea and 8-hydroxyquionoline. All tested doses of thiourea or 8-hydroxyquionoline decreased percentage of grain infection. Generally, thiourea was superior (33.9%) in this respect when compared with either 8-hydroxyquioooline (53%) or the untreated grains (96.65%).