The effect of adding additional amounts of the inorganic constituents normally found in a Morwell coal on the hydrogenation reactions of the coal has been studied. Of the principal inorganic constituents, only iron has a major effect on conversion yields. Addition of iron as haematite led to an increase in coal conversion similar to that obtained by addition of a crushed cobalt molybdate catalyst. Generally, little inorganic matter, even in the case of iron, entered the chloroform-soluble fraction. The variation of conversion yield with the particle size of the coal was examined and found to be small.