Exhaust gas recirculation, EGR, is one of the most effective means of reducing NO, emissions from IC engines and is widely used in order to meet the emission standards. In the present work, experimental investigation has been carried out to study the NO, reduction characteristics by exhaust gas recirculation in a dual fueled engine using hydrogen and diesel. A single cylinder diesel engine was converted to operate on hydrogen-diesel dual fuel mode. Hydrogen was injected in intake port and diesel was injected directly inside the cylinder. The injection timing and injection duration of hydrogen were optimized initially based on the performance and emissions. it was observed that start of injection at 5 degrees before gas exchange top dead center (BGTDC) and injection duration of 30 degrees crank angle gives the best results. The flow rate of hydrogen was optimized as 7.5 Ipm for the best start of injection and injection duration of hydrogen. Cold exhaust gas recirculation technique was adopted for the optimized injection parameter of hydrogen and flow rate. Maximum quantity of exhaust gases recycled during the test was 25% beyond this the combustion was not stable resulting in increase in smoke. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.