Corn is one of the most important crop in the world and also the ideal habitat for the growth of fungi. Their growth on the surface and inside the grain depends on the moisture content and determines its shelf life. The present study attempted to determine the time required for the efficient removal of fungi and aflatoxin contamination of corn grain with 24% humidity. The ozonation process was carried out using the ozone concentration of 2 mg dm^–3 for 15, 30, 60, 120 and 180 minutes. Quantification of fungi was carried out in accordance with PN-R-64791. The total aflatoxin content was tested using the immunoassay – ELISA. The study showed that the use of ozone gas causes nearly one hundred percent reduction in the total number of fungi and aflatoxins produced by them in a damp grain corn. 38% reduction of fungi contamination and 42% in aflatoxin level was observed after 15 minutes of operation. Extension of the contact time for 180 minutes resulted in 99% and 92% reduction respectively. Ozone treatment is effective tool in reducing the microbial load of raw material and is a promising, relatively inexpensive way to protect the raw material before any further processing.