In this paper an efficient and accurate numerical software will be presented. It is based on the Method of Moments in combination with the physical optics (PO) and the geometrical/unified theory of diffraction (GTD/UTD). CAD data of the car body provided by the car manufacturer serves a starting point for an RF computer model. The proposed antenna structures are added to the model as well as additional parameters like the excitation, terminations, real ground, etc.. As a result the surface current density is calculated. This is the basis for all other information like input impedance, near and far field patterns, and gain. The powerful capabilities of the program are demonstrated by means of several latest examples for FM and cellular phone antennas. Very good agreements with measured data show the reliability of the method.