In this study, the production of aflatoxin at a grade appropriate for dietary aflatoxin feeding studies were performed under our laboratory conditions. After sporulation Aspergillus parasiticus NRRL 2999 strain in the tubes containing Patato Dextrose Agar (Merck}, the spores were removed by washings with 0.005 % Triton X-100 (Merck) and an enriched suspensions of spores were obtained, following determination of the spore numbers in per ml ol suspension, the suspension was used the inoculate the sterilized substrate (wheat, corn, rice and peanut) in erlenmeyer flasks and after inoculation the flasks were into an incubator for fermentation at 28 °C. Toplam twelve erlenmeyer flasks each having three ones for each substrate were fermented. At the end of the live days fermentation aflatoxin levels of the flasks were the determined by Fluorescence Spectrophotometry. Aflatoxin levels were measured as mg/ kg substrate (ppm) as follows: 71.88 for wheat (72,55 % B₁, 11.31 % B₂, 11.28 % G₁ and 4.86 % G₂); 48.14 for corn (78.84 % B₁, 7.45 % B₂, 10.85 % G₁ and 2.86 % G₂); 63.64 for rice (83.06 % B₁, 12.98 % B₂. 2.84 % G₁ and 1.12 % G₂); and 14.65 for peanut (84.02 % B₁, 8.82% B₂, 5.01 %G₁ and 2.15 %G₂).