Flash pyrolysis of Morwell brown coal and Wandoan subbituminous coal was performed with three types of pyrolyzers : a Curie-point pyrolyzer in which the secondary pyrolysis of volatiles was suppressed, an entrained-flow reactor in which the primary and the secondary pyrolysis proceeded at the same temperature, and a fluidized-bed reactor that was divided into dense bed and freeboard regions of the primary and the secondary pyrolysis, respectively. The temperature in the dense bed and freeboard regions of the fluidized bed reactor was independently controlled. The yield of mono- and diaromatic products, the most abundant in tar, was adopted as the measure for the reactivity of initial tar generated by the primary pyrolysis, and the role of temperature in the primary pyrolysis zone on the reactivity of the initial tar in the vapor phase was examined. The yield of mono- and diaromatic products for Wandoan coal was not affected by the primary pyrolysis temperature above 600 degrees C but that for Morwell coal was greatly influenced.