Aflatoxin B1 is a secondary metabolite of Aspergillus flavus and Aspergillus parasiticus. It can be formed in commodities before and after harvest. This mycotoxin possesses a variety of toxic effects, potent carcinogen to both animal and human health. Aflatoxin B1 is generally found in feed and food stuff, such as cereal and all products derived from cereals, including processed cereals since it has been proven to be at least partly resistant to food processing methods. Hence, the aim of this study was to determine the possibility of contamination of aflatoxin B1 in food products in Thailand. The 100 food samples were purchased from markets around Bangkok. They were divided into five categories: seven samples of local fermented alcoholic beverages, five samples of imported blue cheese, 18 samples of fermented soybean products, 70 samples of raw peanuts (30) and peanut derived products (40). They were determined for aflatoxin B1 by ELISA method. The revealed rates of aflatoxin B1 contamination were 71.42, 100, 83.33, 86.67 and 90% for the alcoholic beverages, blue cheese, fermented soybean, raw peanuts and peanut derived samples, respectively. The individual values with each category samples, ranged from 0.3 to 2.15 µg/kg (average 0.48 µg/kg), 0.5 to 1.25 µg/kg (average 0.95 µg/kg), 0.2 to 3.2 µg/kg (average 1.54 µg/kg), 0.2 to 8.05 µg/kg (average 6.83 µg/kg) and 0.1 to 73.85 µg/kg (average 5.6 µg/kg) for alcoholic beverages, blue cheese, soybean, raw peanuts and peanut derived samples, respectively.