In a consortium of European industrial partners and research institutes, a combination of industrial development and scientific research was organised. The objective was to improve the catalytic NOx conversion for lean burn cars and heavy-duty trucks, taking into account boundary conditions for the fuel consumption. The project lasted for three years. During this period parallel research was conducted in research areas ranging from basic research based on a theoretical approach to full scale emission system development.NOx storage catalysts became a central part of the project. Catalysts were evaluated with respect to resistance towards sulphur poisoning. It was concluded that very low sulphur fuel is a necessity for efficient use of NOx trap technology. Additionally, attempts were made to develop methods for reactivating poisoned catalysts. Methods for short distance mixing were developed for the addition of reducing agent. Novel catalysts for continuous NOx reduction by fuel hydrocarbons were also developed.As a result of the project two demonstrators were developed: i) one car equipped with a lean-burn naturally aspirated 1.6 litre engine and ii) one 12 litre heavy-duty truck engine. The demonstrators were subjected to European emission test procedures. The car demonstrator achieved 90% conversion with a fuel penalty (low sulphur) of less than 2% in the European driving cycle. For the heavy-duty truck demonstrator, a NOx conversion of 64% was reached with a fuel penalty of 2.4%. However, the catalytic efficiency deteriorated to less than 10% conversion within 8 hours when fuel containing 330 mg Sulphur per kg fuel was used.