Investigation into possibility of fuelling of compression ignition (CI) engine, with an addition of ethanol, was carried out. Ethanol can be a suitable fuel for SI engines, but its application to CI engines requires an assisted ignition. In this work ethanol was injected into the inlet port and entered the engine cylinder mostly as a vapour. Diesel fuel remained a main fuel, but played the role of the ignition fuel. Investigation was carried out on one-cylinder, direct injection CI engine with modified inlet duct for injection of ethanol. The investigations showed that: 1) energy ratio of ethanol to diesel fuel up to 50% can be applied, 2) engine thermal efficiency increased, with the increasing load, 3) soot emission was decreased dramatically after even a small amount of the injected ethanol, 4) emission of greenhouse gas (CO2) was decreased with increasing amount of ethanol, 5) NOx emission was decreased for a small load, but for a high load it is kept at the same level if the engine is fuelled only with diesel fuel. Optimization of the energy ratio of both fuels and injection timing of diesel fuel is being carried out at present.