Mixtures of bis(2-ethylhexyl) succinate and epoxidized soybean oil (ESO) have been evaluated as bio-based plasticizers for poly(vinylchloride). The rate of absorption of the bioplasticizers and their mixtures in the polymer was fast and, unlike that of petroleum-derived plasticizers, did not vary significantly with molecular weight. These bio-derived plasticizers and their mixtures were compatible with the polymer even at high loadings. The succinate was the most volatile and efficient plasticizer, but on heat aging of the polymer compositions, it also had the greatest deleterious effects. Diffusion coefficients and apparent activation energies of formulations containing bioplasticizer mixtures were controlled by the more volatile succinate. Mixtures comprising up to 50 wt% of the succinate yielded acceptably high-tensile properties after thermal aging as well as better plasticization efficiency than the epoxy bioplasticizer. Although the succinate resulted in inferior volume resistivity of the polymer compositions, improvements were obtained with increasing proportions of the epoxidized derivative in plasticizer mixtures. Melt state viscosity-shear rate curves of compositions containing dioctyl succinate (DOS) were similar to those made with two of the petroleum-derived plasticizers, but a DOS/ESO mixture yielded extended non-Newtonian behavior at low-shear rates. POLYM. ENG. SCI., 55:634-640, 2015. (c) 2014 Society of Plastics Engineers