BACKGROUND: The hazardous nature of aflatoxins to human and animals necessitate the establishment of control measures. ObjectiveS: The effect of two medicinal plants, Satureja khozistanica and Satureja macrosiphon, was studied on inhibiting Aspergillus flavus growth and reducing aflatoxin B1-content in the liquid medium. Methods: Essential oils were isolated by hydrodistillation method, using a Clevenger-type apparatus. Various extracts of plant materials were macerated with various extraction solvents (ethanol, ethanol70% and water extracts). Essential oils (0, 62/5, 125, 250, 375 and 500 mg/l) and various extracts (0, 500, 1000, 2000, 4000 and 6000 mg/l) of S. khozistanica and S. macrosiphon were examined for reducing A. flavus growth and it’s AFB1-content in the liquid medium. Amount of aflatoxinB1 was evaluated by high performance thin layer chromatographymethod. Results: Essential oil of S. khozistanica at the concentration of 375 mg/l as well as its ethanol and ethanol 70% extracts at 4000 and 6000 mg/l  respectively caused complete inhibition of fungus mycelial growth, whereas essential oil and extracts of S. macrosiphon couldn’t inhibit Aspergillus growth completely even at the maximum concentration. Essential oils of S. khozistanica and S. macrosiphonia at the concentration of 250 mg/l reduced AFB1-production 98 and 33.52% respectively. Various Extracts of S. khozistanica exhibited stronger anti-AFB1-biosyntesis activity than those of S. macrosiphon, so that, ethanol, ehanol70% and aqueous extracts of S. khozistanica at 4000 mg/l reduced 100, 96 and 32.37% of AFB1-production, respectively. On the contrary, essential oils, ethanol and ehanol70% extracts of both plants couldn’t significantly degrade AFB1-contamination, whereas aqueous extractsof S. khozistanica and S. macrosiphonia at the concentration of 4000 mg/l resulted in degradation of 25 and 32.16% AFB1-content, respectively. ConclusionS: In general, Essential oil and ethanol extract of S. khozistanica considerably inhibited A. flavus growth as well as AFB1-biosynthesis while aqueous extract of S. macrosiphon showed strong AFB1-degradation activity.