TiN/ZrN multilayers deposited by combined de and rf magnetron sputtering on Si substrates have been studied by X-ray diffraction (XRD) and Rutherford Backscattering Spectrometry (RBS). The periodicity of the TiN/ZrN system was determined by the low angle XRD spectra and varied from 5.7 nm to 12.3 nm. These spectra showed a well defined TiN and ZrN layers, but with interfaces not perfectly planar. The individual layers have (111) and (200) orientations perpendicular to the plane of the film. The interfacial roughness was calculated by simulation of the high angle XRD patterns. The rms roughness values ranges from about 3.5 Angstrom or approximately +/- 1.4 atomic plane in the case of samples grown by static deposition mode and about 9.3 Angstrom or approximately +/-3.5 atomic planes in the case of samples grown by rotating deposition mode. With the RES technique it was possible to measure a superior limit for the average roughness.