Phase diagram and chemical activity data, where available, for the Al2O3-Cr2O3, Cr2O3-SiO2, and Al2O3-Cr2O3-SiO2 systems were evaluated and used in the development of models for their thermochemical behavior. Ideal, regular, and subregular solution models were used for the various solid and liquid phases in the Al2O3-Cr2O3 and Cr2O3-SiO2 systems, the Al2O3-SiO2 having been previously modeled using the modified associate species approach. It was possible to model the Al2O3-Cr2O3 liquid as an ideal solution, and compute a phase diagram and activities that resolve previous conflicts. The binary oxide systems were combined into a single set of stoichiometric phases, a corundum solid solution, and a liquid solution to represent the Al2O3-Cr2O3-SiO2 system.