This study examines the usefulness of thermogravimetry in studies of the catalytic hydrogenation of a coal-derived liquid, a complex gas-solid-liquid reaction system, by examining the relative performances of three alumina-supported catalysts, Ni-Mo, Co-Mo and Ni-W. Test samples were heated from ambient temperature to 430 degrees C at 5 degrees C/min in either N-2 or H-2, with or without catalyst. The presence of catalysts reduced the weight loss from the maximum observed i.e. with N-2 and no catalyst, apparently by adsorption of otherwise volatile compounds. Typically volatile components vaporise to about 260 degrees C. From 260 to 380 degrees C, hydrocracking changes from mild to severe (coking) molecular restructuring, the latter dominating beyond 380 degrees C. The evidence suggests that of the three catalysts tested, the Ni-Mo catalyst, which demonstrated the greatest weight loss during the temperature program, was the most beneficial overall.