Effects of Exhaust Gas Recirculation (EGR) on exhaust emissions in an ethanol-fueled direct injection diesel engine have been studied at different injection timings and compression ratios. In addition to regulated emissions the unregulated components formaldehyde, acetaldehyde, and ethanol were analyzed. EGR decreases nitrogen oxide (NOx) emissions substantially and increases carbon monoxide (CO) emission. Total hydrocarbon (THC) emissions, as measured with a flame ionization detector (FID), are fairly constant with increasing EGR rates up to a point where the combustion deteriorates and THC emissions increase rapidly. At low and medium load the emissions of form- and acetaldehyde increase substantially even at EGR rates where THC emissions still are constant. Low aldehyde emissions are favored by advanced injection timing and high compression ratios. The results indicate that the increase in aldehyde emissions due to EGR will decrease under those conditions