A process is described for reducing the oxygen content of a high-oxygen feedstock. The process is particularly suitable for biomass-based feedstocks. The process comprises contacting the feedstock with carbon monoxide and/or coke in the presence of a catalyst. Conveniently, the coke may be present in the form of a deposit on the catalyst. Carbon monoxide may be generated in a regeneration step of the catalyst. The process may be carried out in conventional refinery equipment.