The antifungal activity of Mexican oregano (Lippia berlandieri Schauer) essential oil by gaseous contact on the growth of Aspergillus flavus at selected essential oil concentrations (14.7, 29.4, 58.8, or 117.6 μl of essential oil per liter of air) and temperatures (25, 30, or 35°C) was evaluated in potato dextrose agar formulated at water activity of 0.98 and pH 4.0. Mold growth curves were adequately fitted (0.984 < R(2) < 0.999) by the modified Gompertz model. The effect of the independent variables (concentration of essential oil and temperature) on the estimated model parameters (reciprocal of growth rate [1/ν(m)] and lag time [λ]) were evaluated through polynomial equations. Both ν(m) and λ were significantly (P < 0.05) affected by the independent variables; ν(m) decreased and λ increased as essential oil concentration increased and temperature decreased, which suggests that Mexican oregano essential oil retards or inhibits mold germination stage. Further, minimum fungistatic and fungicide essential oil concentrations at 30 and 35°C were determined. Mexican oregano essential oil applied in gas phase exerts important antifungal activity on the growth of A. flavus, suggesting its potential to inhibit other food spoilage molds.