Process for the production of synthesis gas which involves the steps of: a) preparing a vapor phase mixture comprising steam and at least one hydrocarbon or oxygenated hydrocarbon with an atmospheric boiling point in the range of −50 to 370° C., said vapor phase mixture having a H2O/C molar ratio at least 2, and b) catalytically or non-catalytically converting the vapor phase mixture into synthesis gas, which process is characterized in that the oxygen is only added in bonded form.