The antifungal activity of the oil varied with its concentration and the kind of fungal species, indicating that its activity is proportional to its concentration. The highest activity of the oil was observed against A. niger with an MIC of 15 mg/ml and the highest resistence was observed from A. flavus with an MIC of 118 mg/ml. A. flavus has also been known to show resistance to basil and spearmint oils (Solimana and Bdeaa,2002). However, the inhibition level of the oil against this species in the current study was higher than that of the reference Nystatin indicating that, despite the resistence, the oil is relatively effective. The findings of this study clearly show that the essential oil of C. citratus has antifungal activity and can be used in practical application in the inhibition of mould growth and mycotoxin production in stored grain. It would be important/s and the mode of action of the assential oil against the Aspergillus species. Of interest also would be to determine the effect of the oil on mycotoxin production ability of the moulds.