Fourteen species Aspergillus were isolated by using both blotter and agar medium as recommended by ISTA (1966). A. flavus, A. niger, A. ruber & A. fumigatus were found to be very common on all types of seeds used for isolation. While, species like A. sulphureus, A. glaucus and A. japonicus exhibited their association only with the seeds of some particular crops. The number of Aspergillus species appeared more on storage seeds than on the freshly collected seeds. Aspergillus species showed their association with the other moulds like species of Alternaria, Dreschleria, Fusarium, Curvularia, Cladosporium, Rhizoctonia, Syncephalostrum, Penicillum, Trichoderma and Chaetomium. Hydrolytic enzymes like celluloses, pectinases, amylases, lipases and proteases were studied. Toxin production in vitro and in vivo shows loss in seed germinability due to the association of Aspergillus. Aflatoxin production A. flavus in different agricultural products, its different strains were also studied for their ability to produce aflatoxin in different seeds under the influence of physical and nutritional conditions.