A number of problems were encountered in evaluating catalyst performance in full-range liquefaction recycle solvents containing sizable amounts of resid, unconverted coal and ash. In a liquefaction plant in which only distillate products are produced, resid is recycled to extinction. In such a configuration the feed to the plant will contain a distillate to coal ratio of less than one with the remaining portion of the solvent made up of residual material having reduced donor capacity. In recycle solvents obtained from the Wilsonville pilot plant, which were produced when running in the distillate-only mode, the presence of an insoluble fraction that was easily converted into THF insoluble material was found in the residual fraction of all the Wilsonville recycle solvents that have been tested in our laboratory. When using these recycle solvents for evaluating catalysts, conversion of this residual fraction leads to abnormally high coal conversions even under the mildest of conditions. The presence of catalysts that have accumulated in all of the recycle solvents masks the effect of added fresh catalysts on both dissolution of the coal and 565 degrees C+ resid conversion. Results from this study have shown that catalyst testing in these solvents requires careful control of the components in the residual fraction. Results from liquefaction of Wyodak coal in recycle solvents containing up to 1060 mg freshly added Mo per kg maf coal indicates that coal conversion, pentane solubles and 565 degrees C- distillate yields increase as Mo concentration increases. The activity of recycled Mo is much greater than freshly added Mo. Exceptional activity with nanometer-size iron oxide in the absence of any Mo was also observed.