Application of alternate fuels to diesel engine is much desired. A new and unique dual-fuel injection system has been developed for high speed automotive diesel engines.This system has two features. One is that alternate fuels such as methanol, ethanol and biomass, are directly inducted into the fuel injection pipe through one-way check valve under pressure, and blended fuels are simultaneously injected into the combustion chamber.The other is that various kinds of fuel can be easily adapted to this system not dependent upon the fuel properties such as viscosity.Using a single cylinder direct injection diesel engine and ethanol as an alternate fuel, injection characteristics and exhaust gas emissions were investigated.The results showed that ethanol could replace up to 50% of diesel fuel while keeping the normal engine operating stability. A better fuel economy was also obtained by applying both higher compression ratio and advanced injection timing. NOx concentration was unchanged compared to diesel fuel only.