A flatoxins are extremely harmful and are the most carcinogenic substances known in nature, and as such, affect rice quality to a great extent. This study was undertaken to examine the presence of aflatoxigenic fungi in ten samples of long grain rice obtained from various provinces in Thailand. The rice grains were investigated directly for fungal colonization on agar plates. The major fungal genera detected were Eurotium Syncephalastrum, and Aspergillus Several isolates of Aspergillus flavus, a well-known aflatoxigenic species, were obtained from four rice samples. Aflatoxin production was confirmed in seven isolates using a HPLC 日uorescence detection method. In all isolates, more than 1,000 ng/g of aflatoxin B1 was detected, with 10-30 ng/g of aflatoxin B2 also being detected, whereas aflatoxin G1 and aflatoxin G2 were under the limit of detection.