The reactivity of a mixture simulating a coal liquid from the SRC-II process, with the organonitrogen compounds excluded, was characterized at 350 degrees C and 171 atm; the catalyst was presulfided Ni-Mo/gamma-Al2O3. The reaction products were identified and analyzed quantitatively. Approximate reaction networks were determined for the simultaneously reacting phenanthrene; pyrene, fluoranthene, dibenzothiophene, and dibenzofuran. The reactions in each network are approximated as first order in the organic reactant. The proposed networks allow clarification of pathways that had been proposed earlier with less complete evidence; some previously unidentified pathways have also been identified. The results represent the first determination of quantitative networks of simultaneously reacting compounds in hydroprocessing and help to lay the foundation for modeling of hydroprocessing.