In addition to Aspergillus flavus and A. parasiticus which produce aflatoxin many other toxin-producing fungi have been detected in stored maize in Thailand. It was shown that the aflatoxin content is low at harvest and increases during storage. Field drying and mechanical drying are the most effective measures for controlling aflatoxin contamination in maize. A rapid BGYF test was developed to estimate the aflatoxin level and is being used by many maize dealers. Among the chemicals tested for controlling the causal fungi only a mixed solution of ammonium bispropionate and propionic acid will give temporary control and prevent the growth of fungi in maize under high moisture conditions but will not destroy aflatoxin present before the treatment of the grain. The grain still must be dried. Maize, highly contaminated with aflatoxin, can be detoxified efficiently with ammonia and the resulting grain is safe and can be used for feeding cattle and swine but is not suitable for human consumption and international trade.