The transport sector contributes significantly to the air pollution and particularly influences the local air quality. Beside the question of air quality the transport sectors consumption of fossil fuels and the CO2-emissions from this use is a growing issue. For a long period of time the emissions from light-duty vehicles have been in focus and a lot of measures have been taken to reduce the emissions from these vehicles. The market penetration for light duty diesel cars has been increasing in the most markets in Europe and is now over 30 % (2001). In Sweden, however, the market share for diesel cars has decreased the last three years and is now slightly above 5 %. The issue if petrol or diesel should be used as fuel in passenger cars has been lively debated the last years, at least in Sweden. Specially the particle emissions from diesel cars has been in focus. This study is an attempt to get some more facts to the subject. The study presented in this report is built on new investigations of two petrol and two diesel cars with varying emission control strategies. Tests have been done both in the European driving cycle and in other driving cycles. Beside the regulated substances analysis have been made on non regulated substances as well. Data has also been compared with data from earlier studies.