The effect of cinnamon, clary sage, juniper, lemon and marjoram essential oil (EO) vapours was tested on growth, aflatoxin production and sporulation of Aspergillus parasiticus. In reversed Petri-dish method the sub-lethal EO vapour concentrations ranging from 0.05 to 0.42 mg/cm3 air were used and growth rates (mm/day) and antifungal indices (%) were calculated from the growth curves of the fungus. Aflatoxin production was determined by HPLC and spores were counted in a Burker chamber. Cinnamon, clary sage and marjoram EOs showed concentration dependent growth inhibition. Antifungal index and aflatoxin production using the weak antifungals, juniper and lemon EO, increased in parallel. The same trend was found using cinnamon and clary sage EO vapours up to 0.11 mg/cm3 concentration, and marjoram EO up to 0.21 mg/cm3, while higher concentrations caused a sharp decrease in aflatoxin production. Applying sub-lethal concentrations of EOs might induce stress response in A. parasiticus leading to increased aflatoxin production. Only EO concentrations with strong growth and sporulation inhibitory effect were suitable to inhibit the aflatoxin production of A. parasiticus..