The aim of study is to evaluate the ferment ability of cassava must in the ethanol production process from cassava in Congo. Three traditional methods of ethyl fermentation were tested: spontaneous fermentation, fermentation with yeast inoculation and fermentation led with yeasting and sugaring. Consumption of fermentable sugars was further in the case of directed fermentation with yeast inoculation (3° Brix residual extract from 48 h) compared to spontaneous fermentation without yeast inoculation (3.8° Brixresidual extract from 120 heures). Total sugars have been consumed only partially (66.7% of limit attenuation), while reducing sugars have been almost completely (about 91%). The addition of yeast in the cassava wort have led to a lower assessment of dextrins (2.7% glucose equivalent) compared to spontaneous fermentation (3.6%). It have also assured a better overall ethanol productivity (P_(TE) = 0.83 g ethanol/L.h) than sugaring proceeding (P_(TE) = 0.61 g/L.h) and without yeast additional (P_(TE) = 0.32 g/L.h). Among the fermentable sugars developed in the cassava mash there are reducing sugars, such as glucose and maltose. Non-fermentable sugars represent a significant slice of stock of soluble carbohydrate (on average 3.24% dextrose equivalent) of the must in the three cases of fermentation tested.