SUMMARYFour metabolic inhibitors were tested for their ability to interfere with aflatoxin release at concentrations which did not inhibit growth ofAspergillus flavusin synthetic media as indicated by mycelial dry weight determinations. The amount of aflatoxin B1released in cultures incubated with either N,N-dicyclohexylcarbodiimide or sodium azide was markedly lower than in control cultures. Toxin release was inhibited to a smaller degree by potassium cyanide and 2,4-dinitrophenol at the levels tested. Presence of the latter two inhibitors resulted in a delay of time when peak levels of toxin were released into media. Mycelial extracts from cultures incubated in the presence of N,N-dicyclohexylcarbodiimide contained higher amounts of aflatoxin than did extracts from controls. The results suggest that an energy-dependent transport system is involved in the release of aflatoxins fromAspergillus flavus.