A reactor for autothermal reforming of hydrocarbons that allows a reduction of excess-air factor .phi. during the reforming without resulting in a reduced conversion of the hydrocarbons in an end region of the reaction zone. The reactor includes at least one reaction zone in which is arranged at least one catalyst structure for the reformation so that the educts involved in the reformation are converted while flowing through the reaction zone. A heating device is included for heating the end region of the reaction zone to accelerate the conversion of the hydrocarbons.