A survey of mycotoxin contamination was carried out on a total of 94 samples of cereal grains and products. All samples were collected from commercial sources in Tokyo.Aflatoxin B1, B2 and citrinin were detected together in 11 samples of corn flour in the range of 3.7-37, 2.3-9.9 and 10-98ppb, respectively. In addition, these mycotoxins were detected in 2 samples of corn grains imported from Thailand as raw material for corn flour.This is the first report on the natural occurrence of this mixture of mycotoxins in commercial foods in Japan.It is noteworthy that the samples from Thailand were also contaminated with Aspergillus flavus and Penicillium citrinum.