Hydrogen for fuel cell application can be produced autothermally by the combination of endothermic steam-reforming and exothermic oxidn. of methanol, called oxidative steam-reforming of methanol (OSRM). To enhance this reaction, the novel of a microstructured reactor was developed based on catalytically active metal filaments placed parallel to the reactor walls. The channels for gas flow are formed by the interspaces between strings and have an equiv. hydraulic diam. in the same range of magnitude as the diam. of the filaments. Brass is chosen as support material for its chem. compn. Chromium incorporated by impregnation method provides the best catalyst for OSRM. The microstructure allows amost isothermal conditions in the entire reactor: the max. temp. increase is 3 K and never drops below the entrance value. This demonstrates that heat is efficiently transferred along the filamentous catalysts from the oxidn. part to the exit. [on SciFinder (R)]