The cyanide levels were followed during protein enrichment of cassava by the fungusAspergilus oryzae.The total cyanogen level decreased by 158 mg/kg dry weight to 54.2 mg/kg dry weight as a result of the whole process including fermentation. The cyanogenic glucoside level decreased by 88% during the fermentation process while acetone cyanohydrin was retained in the cassava. The prefermentation processing which involved crushing, sundrying and milling the cassava into flour, reduced the total cyanogen levels by 40%. The process resulted in considerable reduction in the cyanogenic content of the product.