A preliminary study was undertaken to evaluate the effects of mixed solvents and added H 2S on the overall conversions of a moderately reactive coal (Wyodak-2) as defined by tetrahydrofuran solubility. Conversion efficiencies were measured as a function of time and of H 2S concentration in the H 2S-tetrahydroquinoline (THQ) solvent system. The specific solvent systems studied included tetralin and mixtures of tetralin and THQ, with and without H 2S. In all cases, coal conversion was enhanced by the presence of H 2S, THQ or both, relative to the use of tetralin alone. Conversion as a function of THQ concentration was also determined. The relative abilities of the various combinations to effect conversion were found to be as follows: tetralin < 5 wt% THQ-tetralin < 3 wt% H 2S-tetralin < 10 wt% THQ-tetralin = 20 wt% THQ-tetralin < 3 wt% H 2S-20 wt% THQ-tetralin. From these results, it is concluded that both H 2S and THQ operate synergistically to provide enhanced yields of high-quality coal liquids. The relations between conversion, H 2S concentration and nitrogen incorporation are discussed.