Vibration of a car body as an elastic structure is the subject of this research. This report discusses the theoretical basis for experimental procedures, the applied instrumentation and measurement points, the determination of resonant frequencies on the basis of recorded frequency response, mode isolation, determination of generalized masses and damping and stiffness. Starting with the general form of a differential equation, the relationships are developed which define the expressions for the complex power spectrum and can be used for experimental determination of the vibratory characteristics of the car body.Using 5 points of excitation and 80 points at which accelerations are measured, the complete car body is covered. Resonant frequencies are determined separately for the roof, left front and rear fenders and floor of the car body. In this report, criteria and procedures for isolation of vibration modes, along with the closely connected determination of the eigen form of vibration for different assemblies of the car body are presented. Applying the complex power method, the generalized mass, damping and stiffness of isolated modes are determined.