The successful use of single-crystal alloys in IGT applications is contingent upon overcoming processing problems such as defect formation, and maintaining microstructural stability once in service.  The present work uses a design approach aimed toward the development of a set of alloys for industrial gas turbine application. In the hopes of better understanding elemental variation effects on the aforementioned material properties, a baseline alloy composition named the baseline ‘Model’ alloy (based on CMSX-4 and PWA 1483) was used as the foundation from which two iterations of ‘elemental variation effect’ evaluations were conducted (‘Phase I’ and ‘Phase II’).  The thermodynamic equilibrium module in the JMatPro Program was utilize to evaluated ‘Phase I’ and ‘Phase II’ theoretical property trends and determine chemistry modifications to the baseline ‘Model’ alloy.  Five variant alloy compositions were tailored using JMatPro modeling techniques and were laboratory tested for validation purposes.  To address the effects of additions previously shown to influence hot corrosion and material stability, final compositions incorporated characteristic variations of Al/Ti ratio (with Ta variation), Cr (with Al and Ta variations), and Re content for comparison.  This study evaluates the computational capabilities of the JMatPro thermodynamic equilibrium module to predict material properties related to defect formation and microstructural stability.  Through computational techniques this work also contributes to a better understanding of elemental variation effects on microstructural stability, phase transformation temperatures, and material segregation behavior to facilitate the development of better alloys for future single crystal IGT use.