A coal hydrogenation model has been formulated which incorporates both chemical and microscopic experimental data. In this generalized model, carbonization and hydrogenation areviewed asconcurrent processes in the liquefaction of coal. Insufficient hydrogen availability, rapid heating rates and long reaction times at elevated temperatures can promote carbonization reactions. The model describes in detail the reaction pathways involved in the hydrogenation of both inertinite and vitrinite. When vitrinite is hydrogenated in the presence of a hydrogen donor solvent, a plastic material called vitroplast is formed. The vitroplast is either converted to liquid and gaseous products when hydrogen availability is high or becomes mesophase and then semicoke when hydrogen availability is low. Even under favourable hydrogenation conditions, the major reaction pathway in the hydrogenation of inertinite is one of initial mild carbonization followed by hydrogenation. It is evident that the difference in hydrogenation behaviour between vitrinite and inertinite is due, in part, to the ability of the hydrogen donor solvent to penetrate vitrinite but not inertinite particles. The hydrogenation model is useful for explaining various phenomena that occur during hydrogenation, such as the formation of mesophase and semicoke, and the blockage of reactors and preheaters.