Because of the potential health risks of aflatoxin B 1 (AFB 1 ), it is essential to monitor the level of this mycotoxin in a variety of foods. An indirect competitive immunoassay has been developed using the NRL array biosensor, offering rapid, sensitive detection and quantification of AFB 1 in buffer, corn and nut products. AFB 1 -spiked foods were extracted with methanol and Cy5-anti-AFB 1 added to the resulting sample. The extracted sample/antibody mix was passed over a waveguide surface patterned with immobilized AFB 1 . The resulting fluorescence signal decreased as the concentration of AFB 1 in the sample increased. The limit of detection for AFB 1 in buffer, 0.3ng/ml, was found to increase to between 1.5 and 5.1ng/g and 0.6 and 1.4ng/g when measured in various corn and nut products, respectively.