The thermal oxidative stability was evaluated for 7 high oleic acid sunflower (HOSO) and polyunsaturated soybean oil (PUSB) blends ranging from 0.0% to 100.0% of each vegetable oil. Each blend was evaluated in quadruplicate over an eleven day period with 300 minutes of heating at 180°C per day. Thermal oxidative stability was determined by changes in peroxide values (PV), fatty acid and triglyceride composition, and percentage of major volatile products (%MVP). A 2 Way ANOVA, simultaneous confidence intervals, trend analysis, and Paired t-Test, each with a set p value of (0.01) were used for the statistical analysis. The triolein (OOO), trilinolein (LLL), and fatty acid contents were significantly different (p< 0.01) between each blend before and after heating, with the exception of stearic acid levels, which were not significantly different between each blend. Thermal stability increased for the triglycerides and fatty acids as the degree of saturation increased: (Saturated > Monoenic > Polyenic). The addition of HOSO to PUSB increased the thermal oxidative stability of all the blends when compared to the 100% PUSB. The PV and %MVP increased as the levels of OOO decreased and the levels of LLL increased in the blends. The blends with a (1:1) ratio of each vegetable oil experienced a unique breakdown pattern. The monoenic fatty acid levels decreased and the polyenic fatty acid levels increased for this blend only. Overall, blends with 10% to 75% HOSO addition performed equally as well in the thermal oxidative stability testing. / Master of Science