During the past years most fundamental research worldwide has been concentrated on the direct injection diesel engine (DI). This engine has a lower specific fuel consumption when compared to the indirect injection diesel engine (IDI) used up to now in most passenger cars. But the application of the direct injection engine on passenger cars and light trucks has various problems. These are associated mainly with its ability to operate at high engine speeds due to the very low time available for combustion. To overcome these problems engineers have introduced various techniques such as swirl and squish for the working fluid and the use of extremely high pressure fuel injection systems to promote the air-fuel mixing mechanism. The last requires the solution of various problems associated with the use of the high pressure and relatively small injector holes. On the other hand the IDI diesel engine even though having higher specific fuel consumption compared to the DI engine has various advantages. The NOx emission levers are relatively low and the power concentration is high since it can operate at lower air/fuel ratios and at higher engine speeds. Furthermore the IDI engine does not require sophisticated fuel injection systems since the injection pressure level is low. As far as particulate emissions are concerned the IDI engine has in most cases comparable or even lower values compared to the DI engine. Taking into account the previous and the fact that the IDI engine is very reliable it seems that it will continue to exist in the future. For this reason in the present work are given the initial results obtained from a newly developed three-dimensional multi-zone combustion model for IDI diesel engines. The model considers in general two major control volumes the main chamber and the prechamber. Inside the swirl prechamber the interaction between the injected fuel and the air has been considered using the conservation equations of mass, energy and momentum. Using the proposed 3-D multi-zone model we are in position to describe the mixing and combustion mechanisms inside each chamber and to estimate the local pollutants formation history and the distribution of various thermodynamic parameters. To validate the model an experimental investigation has been conducted on a Ricardo E-6 IDI single cylinder test engine having a swirl type prechamber. The comparison of experimental findings and computational results up to now reveal a good degree of agreement for both engine performance and pollutants emissions and the model seems promising. This is encouraging, especially if we take into account the complexity of the new concerning the history of emitted pollutants and the contribution of each chamber, the main chamber and the prechamber to their formation.