A method of controlling a circulating fluidized bed gasifier includes feeding first and second portions of particulate material to be gasified through inlets in a gasifier. Oxygen and steam are fed through a bottom grid into a lower portion of the gasifier to fluidize the bed. Product gas and entrained particles are discharged from an upper portion of the gasifier. Particles are separated from the product gas and a portion of the separated particles is returned to the lower portion. A portion of the returned particles is oxidized to generate heat. Heat and oxidizing products from the lower portion are transferred to the center portion to generate the product gas. A ratio of the first and second portions of particulate material to be gasified is determined on the basis of a measured temperature profile so as to control the vertical temperature distribution in the gasifier.