Rutherford Backscattering Spectrometry (RBS) and Electrical Resistivity Measurements (ERM) were used to investigate the mixing of Au/Ge bilayer deposited onto glass substrate induced by Ar ions. Mixing was initiated by bombarding the sample with 400 keV Ar-40(+) beam with a fluence up to 1.2 x 10(17) ions/cm(2) at a constant flux of 0.25 mu A/cm(2). To assist the evaluation of the experimental results, all spectra were simulated using "RUMP" computer code. RBS results indicated that ion beam mixing led to a formation of AuGe2 compound. The mixed region was noticed to increase with the gradual increase of Ar+ fluence. Results were also compared with current theoretical models used to describe the mixing process. The Borgesen thermal spike model was found to accurately predict the diffusion in Au/Ge interface. An increase in the electrical resistivity of the film was detected during Ar+ irradiation.