The group contribution viscosity model for pure coal model liquids described in a previous paper (Energy Fuels 1995, 10, 333) has been successfully extended to binary liquid mixtures of coal model compounds, and a procedure has been developed to use the model for computation of viscosities of coal-derived liquids. It is shown that simple mixing rules, or even a pseudopure component model, is adequate to estimate mixture viscosity within reasonable accuracy for these compounds. For application of the model to coal-derived liquids, a data set on SRC-II coal liquid cuts available in the literature has been used. Sufficient chemical analysis data were available for these cuts to make the application of our model possible. The computational procedure involved transformation of the analytical data into functional group characterization of the coal liquid. Central to this procedure was the definition of types and distributions of various ring structures in multiring compounds. When compared to limited studies available in the literature, this model predicts viscosities of coal liquids with better accuracy. Overall, this is the first viscosity model that has been developed for the type of structures that exist in coal-derived liquids, and provides a reasonably accurate procedure for computation of viscosities of narrow boiling coal liquid cuts, a property that is necessary in designing efficient coal liquefaction processes.