The motivation for the work described in this paper was conflicting results from diesel engine research on the question of whether the structure of an oxygenated compound blended into diesel fuel can affect the level of reduction of particulate emissions. A constant-pressure reactor model (SENKIN) was used to investigate the effect of oxygenated additives on aromatic species, which are known to be soot precursors, in fuel-rich ethane combustion. 5% oxygen by mass of the fuel was added to ethane using dimethyl ether (DME-CH3OCH3) and ethanol (C2H5OH). A significant reduction in aromatic species relative to pure ethane was observed with the addition of both DME and ethanol, but DME was more effective in reducing aromatic species than ethanol. One reason for the greater effectiveness of DME was found to be its higher enthalpy of formation, compared to ethanol, which led to a higher final temperature. However, with initial temperatures adjusted to achieve the same final temperature for all fuels, DME was still more effective than ethanol in reducing aromatic species compared to the base case of pure ethane. A reaction flux analysis was conducted to determine the mechanism of aromatic species reduction by the oxygenated compounds and the cause of the greater effectiveness of DME. 0 2003 The Combustion Institute. All rights reserved.