Although water injection or water/fuel emulsions are a well known method of reducing NOx in stationary Diesel engines, their influence on Diesel particulates and particulate SOF has recieved little study. A single cylinder DI Petter engine was used to investigate the influence of Diesel/water emulsions on particulate emissions and associated gaseous emissions. Water/fuel ratios of up to 20% were used and a strong influence on emissions was found. Both NOx and particulate emissions were decreased with increased water content. However, there was a major increase in the unburnt hydrocarbons. Associated with this was a similar increase in the particulate solvent organic fraction and of the PAH fraction of this. These effects on UHC and PAH emissions make Diesel/fuel emulsions an unattractive solution to the Diesel NOx and particulate emissions problems.