The development of today's drivetrains focusses on the reduction of vehicles' CO2-emissions. Therefore, a drivetrain for urban and commuter traffic is under development at the Institute of Internal Combustion Engines. The concept is based on a lean-burn air cooled two-cylinder natural gas engine, which is combined with a hydraulic hybrid system.On the one hand, lean-burn combustion leads to low nitrogen oxides emissions and high thermal efficiency. On the other hand, there are several challenges concerning inflammability, combustion stability and combustion duration. An approach to optimize the combustion process is the design of the piston bowl.The paper presents the engine concept at first. Afterwards, a description of design parameters for pistons of natural gas engines and a technical overview of piston bowls is given. Subsequent to the analysis of the different piston bowls, a new design approach is presented. Different geometries are discussed concerning their suitability for the use in a two-cylinder natural gas engine. The piston bowls are evaluated by three dimensional computational fluid dynamics (3D-CFD) simulations. Afterwards the results of measurements at the engine test bed are shown.Altogether, the paper describes design, geometry optimization, 3D-CFD-simulation and test bed results of a new piston bowl design for a small lean-burn natural gas engine.