A study of MoS2 catalyst recycle during slurry-phase hydroconversion of residue oil, under high hydroconversion conditions, is reported. Different concentrations of MoS2 (100, 300, 600, and 1800 ppm derived from Mo-micelle and Mo-octoate precursors) were investigated in a semibatch stirred reactor. Catalyst. recycle was simulated by reusing the solid coke-catalyst recovered from the reactor in subsequent experiments. The process was repeated several times until the catalyst deactivated. The recycled catalyst had a very similar activity to the fresh catalyst in the early stages of recycling. Experimental results showed that with increased catalyst concentration, an increased number of catalyst recycles with acceptable coke yield (<3 wt %) and toluene insoluble organic residue (TIOR) conversion (>80 wt %) were possible before deactivation was observed. At an initial concentration of 600 ppm Mo (using both Mo-micelle and Mo-octoate precursors), the catalysts were recycled 3 times without any significant loss in catalyst activity. Characterization of the recycled coke-catalyst mixture recovered after each recycle showed that coke aging resulted in significant changes to the properties of the recycled coke. While the MoS2 catalyst was well-dispersed within the coke matrix, the coke's initial, amorphous structure transformed to a more graphitic structure as the number of recycles increased. These change's resulted in catalyst deactivation during hydroconversion.