Abstract A kinetic study of the pyrolysis of municipal solid waste (MSW) in a fluidized bed reactor was carried out. The MSW pellets are discharged onto the fluidized sand bed; in the upper part of the reactor the volatiles evolved from primary reactions underwent secondary cracking reactions. A correlation model was applied to simulate the primary and secondary reactions as well as the heat transfer process. The experimental yields of the total gases obtained in 49 runs performed at 700, 750, 800 and 850 °C fitted satisfactorily using a flexible simplex method. The values of the kinetic parameters of secondary reaction, the heat transfer coefficient from the bed to the sample and the ratio “secondary gas yield/primary tars yield” were optimised. The values of the secondary kinetic parameters, which showed a great inter-relation with those of the primary reactions, were within the range of the values proposed in literature for other biomass tar cracking.