A mathematical model for spontaneous combustion of coal has been developed that takes into consideration the moisture content of coal. The one-dimensional non-steady-state model consists of conservation equations for oxygen, water vapour, inherent moisture of the coal, and energy for both gaseous and solid phases. A first-order Arrhenius reaction rate for oxidation under pore diffusion and chemically controlled reaction regimes is considered. The rate of evaporation or condensation is also considered as a function of particle size, isothermal temperature of coal particles, energy of water-coal bonding and water content of coal and gas streams. The equations of the model have been solved numerically by finite-difference technique, and the influences of gas velocity, particle size and inherent moisture content on the process of spontaneous heating have been examined parametrically.