The present invention relates to a process for the production of ethanol and butanol from biomass, and in particular to a process for the production of ethanol and butanol using two separate fermentation steps, said process comprising: a) passing a biomass feedstock to a first fermentation step, b) in said first fermentation step subjecting the biomass feedstock to anaerobic fermentation at a pH below 6.0 and at a temperature in the range 20 to 700° C. and so as to convert the biomass to a product predominantly comprising acetic acid and butyric acid with at least a 2:1 ratio by weight of acetic acid to butyric acid, c) treating the product stream of step (b) to separate a solution comprising the acetic acid and butyric acid by: (i) separating a solution comprising the acetic acid and butyric acid from any residual solids and (ii) separating bacteria and/or pasteurising or sterilising the solution from the first fermentation step, and d) in a second fermentation step fermenting the solution comprising the acetic acid and butyric acid from step (c) to form ethanol and butanol.