The partial oxidation of methane to synthesis gas over Ni/alpha-Al2O3 catalysts. (1 and 5 wt.-% Ni loading, 71-160 and 250-355 mu m particle diameter) was investigated in different types of fluidized-bed reactors, i.e., the bubbling fluidized bed (FIB), the spout fluid bed (SFB) and the internally circulating fluidized bed (ICFB), A methane-to-oxygen ratio of 2:1 was used in all experiments and the temperature was varied between 700 and 800 degrees C. Gas velocities and catalyst masses were adjusted to assure a stable and controllable reactor operation. A nearly isothermal operation was established in all reactors. The thermodynamic equilibrium values were achieved in the FIB and SFB reactor whereas in the ICFB reactor slightly lower conversions and selectivities were obtained. Taking the direct scale-up concept of the ICFB reactor into account, significant higher space-time yields were obtained in this reactor than in the industrial-scale bubbling fluidized-bed reactor. No increase of the space-time yield in comparison to the FIB was obtained in the SFB reactor.