A calculation of the Fe-Th phase relationships was undertaken in order to develop a self-consistent description of the system. A subregular solution model was used to describe the solution behavior. Intermediate phases were treated as composition invariant. Due to the limited availability of experimental thermodynamic data, a multi-step analysis was employed to develop a better description of the thermodynamic properties in the system;As a quantitative guide to the glass forming ability (GFA) in the Fe-Th system, T[subscript]0 and TTT curves were evaluated from the previously derived thermodynamic description of the system. From the TTT curves, critical cooling rates (R[subscript] c) to avoid crystallization were determined. Since the Fe-Th system has several solid phases, the relative stability of each phase in the metastable region is discussed. Kinetic parameters such as viscosity ([eta]), glass transition temperature (T[subscript] g) and interfacial energy ([sigma]) were estimated since experimental values were not available;This analysis indicates that thermodynamic data alone can not be relied upon to predict the phase boundary behavior. Both thermodynamic data and phase diagram data should be used.