Abstract A set of five coals have been electrochemically hydrogenated and changes to the chemical structure were monitored by elemental analysis and NMR. It was thought that the elemental analysis gave spurious results due to possible hydrogen trapping. The NMR clearly showed a decrease in aromatic material and the creation of aliphatics. Changes to the macromolecular structure following hydrogenation were monitored by measuring changes in: the amount of pyridine soluble material; the amount of volatile material; decrease in glass transition temperatures; and in solvent swelling. The increase in the amount of aliphatic material correlated well with the change in the amount of soluble material and decrease in glass transition temperature. A less perfect correlation was noted between the amount of aliphatic material and the amount of volatile material and no correlation was noted between increase in aliphatics and solvent swelling.