Diesel engines running in a dual-fuel fumigation mode using injection of a high volatility fuel into the intake air and direct injection of diesel fuel can reduce NOX and particulate matter emissions. Fuels such as methanol, hydrogen, gasoline, and anhydrous ethanol have been studied as fumigants; however there has been less published regarding the use of high water content hydrous ethanol. Current production of ethanol yields anhydrous (200 proof) ethanol with no water content. The distillation and dehydration processes used to remove excess water from fermented starches during production require large amounts of input energy, reducing the renewability of the resulting fuel. This paper describes an experimental investigation of an aftermarket fumigation system provided by CleanFlex Power Systems, LLC. Experiments to measure gaseous and particulate emissions were conducted using 120 proof hydrous ethanol and nonoxygenated ultra-low sulfur diesel fuel. A John Deere 4045HF475 Tier 2 engine was modified to incorporate the fumigation system in the intake plumbing downstream of the charge-air cooler, just prior to the intake manifold. Data was collected for dual fuel fumigation combustion and compared to diesel only combustion. This study shows that the fumigation system achieved lower levels of NO X and soot proportional to the fumigant energy fraction (FEF), but increased CO and hydrocarbon levels as compared to dieselonly combustion modes. The results suggest that increasing the FEF by using lower water content or better mixing through port-injection may increase the emissions reduction potential of hydrous ethanol fumigation.