This study presents the results of exhaust gas recirculation (EGR) and cyclonic separator for simultaneous oxides of nitrogen (NOx) and particulate matter (PM) reduction in a direct injection (DI) diesel engine under different engine loads and speeds. There is a significant NOx reduction by EGR, but PM is hugely increased, especially at high EGR rate-high load conditions. A significant reduction in PM is achieved by the use of cyclonic separator without deteriorating other emissions. At high speed-high load conditions, the cyclonic separator has a greater efficiency. Both NOx and PM reduce simultaneously when EGR and cyclonic separator are used together. Using cyclonic separator with high EGR rates, a remarkable NOx reduction is possible keeping the PM level significantly lower than non-EGR level.