A comprehensive reactor model of the oxidative coupling of methane to higher hydrocarbons (OCM) in a fluidized-bed reactor was developed. Bed hydrodynamics was described according to a modified version of the "bubble assemblage model" of Kato and Wen (1969, Chem. Enyng Sci. 24, 1351-1368). The chemical reactions were characterized by two separate kinetic models for heterogeneous and homogeneous networks. The model was validated on the basis of experimental results obtained over a La2O3/CaO catalyst in laboratory-scale fluidized-bed reactors (ID = 5 and 7 cm). Conversion of methane and C-2+ selectivity were predicted with accuracy +/-20% in a wide range of reaction conditions (X(CH4) = 8-39% and S-C2+, = 25-74%). The simulation results confirmed the importance of consecutive reactions and gas-phase reactions which are in a fluidized-bed reactor promoted by the bed hydrodynamics.