In anticipation of ever tighter noise emission limits for motor vehicles it is necessary to reduce the noise emitted by diesel engines.Within the program “Road Noise Abatement” a new heavy-duty air-cooled DEUTZ diesel engine was developed. This is a 6-cylinder, in-line, turbocharged and intercooled engine, with a power output in excess of 200 kW. The development program, conducted by Kloeckner-Humboldt-Deutz AG (KHD), was partly funded by the Ministry of Research and Technology of the Federal Republic of Germany. Objective of the program was to demonstrate compliance with the 1990 EC drive-by acceleration noise limits without the need for special noise abatement measures on the vehicle. While meeting these noise requirements, the diesel engine had also to comply with the future European emission standards (50% below ECE R 49) and deliver the excellent performance and fuel economy characteristics typical of this type of engines.This paper describes the measures undertaken with the objective of reducing the combustion noise as well as the noise generated by critical engine assemblies such as crankcase, gear train and cooling system. It shows that a consequent development work on the combustion system combined with basic noise analysis allows for compliance with US noise and emission standards applicable to the 1990s.