A study was undertaken to evaluate the effect of process parameters on the liquefaction of swelled Black Thunder mine (WY) subbituminous coal with the introduction of soluble catalyst precursors. The process concept involved simultaneously swelling coal with a hydrogen bonding solvent and impregnating coal with a soluble catalyst precursor with subsequent liquefaction at 410 degrees C in a hydrogen atmosphere. The parameters included reaction solvent, swelling solvent and its interaction with various catalyst precursors, and the type, loading, and method of introduction of the catalysts. Interactions among the parameters were evident. Of particular significance, the swelling solvent and its interaction with the catalyst precursor affected coal conversion. Adjusting the various parameters did not increase coal conversion relative to the conversion achieved when the catalyst precursors were added directly to the liquefaction feed slurry.