An investigation has been performed of some of the characteristics of di-methyl ether (DME) during high pressure injection in a diesel fuel injection system with a single hole nozzle. Recent developments in the use of DME as an alternate fuel for diesel engines are discussed. The effects of fuel compressibility on compression work are compared for DME and typical hydrocarbon fuel components. Photographs of the transient injection process into room temperature Nitrogen are given for a range of chamber pressures. For a single hole injector, spray penetrations can be predicted using existing correlations for diesel fuel, provided DME fuel properties are used.