:The state of discussion on the new Euro III exhaust gas limits which have not been fixed yet and the test procedure will be presented.The development target at Mercedes-Benz is not only to reach the future limits reliably in standard production before they come into force but also to have the largest possible customer benefit, i. e. in particular favourable manufacturing costs and high fuel economy. An entirely new generation of engines is developed for this purpose.One essential point in this context is the injection system. Mercedes-Benz decided to develop new unit injection pumps with electronically actuated solenoid valves in conjunction with ordinary nozzle holders for high pressure levels, which feature advantages as compared to the known unit injector system. A common rail system providing further potential for a reduction in particulates constitutes an alternative. Particularly high requirements are placed on particulate emission in conjunction with exhaust gas recirculation if the latter is introduced in order to achieve low NOx values with the lowest possible influence on consumption.Combining the exhaust gas turbocharger with a mechanically driven turbocharger is yet another possibility to reduce particulates and at the same time enhance starting-off and torque characteristics.In addition to reducing NOx through in-engine measures, work is performed on a post-engine NOx removal process which also aims at optimum consumption.In order to have the best solution available as early as possible, various systems are developed in parallel at Mercedes-Benz. This multiple strategy requires highly efficient development structures to keep effort and expenditure at an acceptable level.Yet another development challenge is to achieve lower costs for the new engines as compared to their predecessors although they are worth more in terms of technology.