Moniliformin (MF) was determined quantitatively for 123 samples of rice and corn collected from the areas with Keshan disease in Sichuan and Yunnan provinces and the areas without Keshan disease in Beijing using thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Results showed MF was found in 8.8% of the 83 rice samples from the areas with the disease, ranging from 73.5 to 265.3 micrograms/kg, and in 2.5% of the 40 sample from the areas without the disease with an average of 179.5 micrograms/kg. MF was found in 81.4% of the 43 corn samples from the areas with the disease, ranging from 52.3 to 1116.0 micrograms/kg, and in 9.7% of the 61 samples from the areas without the disease ranging from 73.3 to 1082.2 micrograms/kg. There was significant difference between positive proportions for MF in rice and corn from the diseased and non-diseased areas, but no significant difference between their average amount of MF. Differences in contamination of MF between rice and corn was much greater than that between different areas.