As the largest public transport operator in Germany, with approximately 1,400 buses, the BVG is obliged to set standards, even in the area of environmental protection. Until such time as the fuel cell series gas been completed and zero emission buses have been introduced, the BVG is using sulphur-free city diesel buses as recommended for implementation by the EU from 2005 and it has already started installing Continuously Regenerating Trap (CRT) exhaust filters within its entire fleet. The use of the CRT filter system, consisting of an oxidizing catalytic converter and a smoke filter, ultimately reduces the particle amount to a detectable limit and contributes to the substantial reduction of other pollutants. Furthermore the BVG is currently carrying out tests using aquazole fuel for buses. In addition to this, a hybrid series bus has successfully been tested for the past three years on a specific route in Berlin. From a technical viewpoint this entails using a lead battery as brake energy input. Under certain operational strategies interim results have shown that it is possible to achieve a 15 % reduction in fuel consumption. This technology is state-of-the-art for the anticipated future incorporation of fuel cell technology within the BVG's fleet. In order to thus support the development of a pollutant free and particularly quiet bus the BVG is currently participating in a fuel cell bus project under an EU programme. The paper is structured as follows: - introduction to the BVG's activities and aims; - CRT (Continuously Regenerating Trap); - Auquazole (diesel water mix); - Project 'Hybrid Bus': Bus technology, operational experience, fuel consumption, future development; - Project 'Fuel Cell Bus'.