A method for the autothermal reforming of a hydrocarbon, in particular of diesel, includes introducing a combustible mixture of the hydrocarbon to be reformed and an oxygen-containing medium into a first reaction zone of a reformer, A gas-phase reaction is ignited. After an operating temperature required for the autothermal reforming process is reached, water or a water-containing medium is introduced into the first reaction zone, and the water content is increased until the conditions for the reforming process of the hydrocarbon prevail. The reforming process then takes place predominantly in a second reaction zone.