The paper describes the details of an interactive piston development program (C.A.E.), especially its new methods of piston design in relationship to oil consumption and blow-by. Based on a library of emperical design standards the preliminary design scheme of a piston is carried out interactively. The drawing is generated automatically by the computer. The design process will be continued by a cycle simulation providing all gas related data, such as heat transfer coefficients, temperature and pressure of gas at each crank angle. Using an interactive preprocessor the engineer creates economically by direct communication a three dimensional mesh for Finite Element (F.E.) calculation. For two truck diesel engine pistons detailed results from the F.E. program are presented. After modification and additions relating to the particular engine the computer produces the prototype drawing.