The phase chemistry and thermodynamics of the Ti-Si-N system are reviewed leading to a revision of the ternary phase diagram at 1273 K to include the extended compositional ranges of δ-TiNx and Ti5Si3(Ny) and the compounds Ti3Si, Ti5Si4, and α-Ti. This same information is presented in the form of phase stability diagrams which plot the stability criteria for each phase as a function of thermodynamic activity of one component and the relative composition of the other two components. Plots in terms of log asi vs Ti/(Ti + N), log aN2 vs Si/(Ti + Si), and log aTi vs N/(Si + N) were constructed. All diagrams are consistent with current knowledge of phase compatibility and, therefore, are topologically correct. Further refinement will be possible as more accurate information on thermodynamics and compositional limits of solid solutions becomes available.