The effect of some food preservatives, such as sorbic (SA) and propionic (PA) acids, on aflatoxin production in synthetic media or in moistened (20%) wheat seeds, was investigated. The preservatives tested, added to synthetic media at sublethal concentrations both at the inoculum and after 5 days of incubation, stimulated aflatoxin production byAspergillus parasiticus.Sorbic and propionic acids are metabolized by the fungusin vivoandin vitro.Lower concentrations of PA and SA (0.05 to 0.1% w/w) in wheat seeds are ineffective against both fungal growth and aflatoxin production, whilst the combined use of butylated hydroxy toluene (BHT), and PA or SA was more effective in controlling aflatoxin production than their use as single components.