Thirty seven strains of the Aspergillus flavus group isolated from animal mixed feeds have been screened for their ability to produce aflatoxins in yeast extract and sucrose (YES), aflatoxin producing ability (APA), and coconut agar medium (CAM) media. The concentration and detection of the aflatoxins by different methods is compared. Five known aflatoxin-positive and one aflatoxin-negative strains have been used as controls. Only 5 out of the 37 strains (13.5%) were aflatoxin-producers in YES medium. Of these five strains and the five known aflatoxin-positive strains, only three showed blue fluorescence in APA medium and four in CAM medium. Generally, the aflatoxin concentration in CAM medium was higher than in YES and APA media. Using the 'agar-plug method' and by direct spotting of the YES broth on TLC plates, some aflatoxin-producing strains were not detected.