Vanadium and nickel-based carbonaceous solids derived from the controlled burning of coke/ bottoms/resid have the potential to serve as attractive catalysts in slurry-based upgrading processes. Carbonaceous solids comprised of a high concentration of metals, namoly, Venturi fines (solids obtained from an ExxonMobil flexicoker unit and containing similar to12 wt 17( total metals) and flexicoker ash (prepared from the mild burning of Venturi fines and gasifier bed coke and containing similar to50 wt% total metals) were more effective slurry catalysts than those comprised of less than 5 wt % total metals. Analyses of the hydroconverted products produced from slurry hydroprocessing autoclave experiments indicated that at 8 wt % solids in the feed sulfided Venturi and flexicoker carbonaceous catalysts were comparable on a once-through and recycle basis. However, on the basis of catalyst performance versus total metals dispersed in the feed, Venturi fines were superior to flexicoker solids. X-ray diffraction analysis of the source flexicoker solids suggest that the primary metal species was vanadium pentoxide. If treated with elemental sulfur/ H-2(g) at elevated temperature and pressure the oxide formed active metal sulfide catalysts. Possible reaction pathways for the in situ formation of the metal sulfides are proposed. Upon recycling, carbonaceous catalyst solids were less effective in producing hydroconversion products of similar quality to those achieved on a once through basis. Carbonaceous material deposited on the catalysts during the hydroconversion process were removed via mild calcining to regenerate the solids and experimental data clearly indicated that the catalyst activity of the calcined solids was not restored to that exhibited by fresh sulfided solids. A reduction in surface area of the solids upon calcining was observed and is suggested to contribute to catalyst deactivation.