Laws concerning emissions from heavy duty (HD) internal combustion engines are becoming increasingly stringent. New engine technologies are therefore needed to satisfy these new legal requirements and to reduce fossil fuel dependency. One way to achieve both goals is to partially replace fossil fuels with alternatives that are more sustainable with respect to emissions of greenhouse gas, particulates and NOx. Therefore a dual fuel direct injection HD engine using ethanol or methanol as the main fuel with a pilot diesel injection to facilitate ignition was studied. The objective of this investigation was to find practical ways of combining the established advantages of Diesel engines, such as high fuel efficiency, with the advantages of alcohol fuels such as lower particulate emissions, bypassing the NOx-soot-trade-off. Furthermore, this study serves as a proof-of-concept, demonstrating that methanol and ethanol can successfully be used in a high pressure Diesel injection system. The experiments were conducted on a single cylinder HD engine in order to study the combustion efficiency and emissions for a range of load points. The test engine used in this work utilized production components wherever possible. Hence two standard common rail Diesel injection systems were used together with a newly designed cylinder head and adapted injection nozzles. Injection pressures on the alcohol side were varied up to 1500 bar. The results at different load point show comparable or even higher combustion efficiencies compared with the same HD engine running on Diesel fuel, whilst the emissions of particulates and NOx were lower, even though the system was not optimized towards emissions reduction.