This paper expands the consideration of the factors affecting the nanostructure and oxidative reactivity of diesel soot to include the impact of exhaust gas recirculation (EGR). Past work showed that soot derived front oxygenated fuels Such as biodiesel carries some surface oxygen functionality and thereby possesses higher reactivity than soot front conventional diesel fuel. fit this work, results show that EGR exerts a strong influence oil the physical properties of the soot which leads to enhanced oxidation rate. HRTEM images showed a dramatic difference between the burning modes of the soot generated Under 0 and 20% EGR. The soot produced under 0% EGR strictly followed all external burning mode with no evidence of internal burning. In contrast, soot generated Under 20% EGR exhibited dual burning Modes: slow external burning and rapid internal burning. The results demonstrate clearly that highly reactive soot call be achieved by Manipulating the physical properties of the soot via EGR. (C) 2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved.