The range of composition (x) is one of the parameters we often have to measure if Si1-xGex layers are generated by chemical vapour deposition (CVD). It is important in this case, in which way the optical properties of Si1-xGex layers depend on the range of composition. We are interested in using multi-wavelength ellipsometry as a technique for rapid, nondestructive characterization of these samples, without large preparations, especially for series of measurements (2D profiles or wafer-lots). The number of unknown parameters and the multiple solutions are reduced by using several wavelengths during the measurement. The calculation is prepared by the help of parameter-correlation based on results of spectroscopical ellipsometry. To examine the results, thickness and composition were controlled for selected samples by cross-sectional transmission electron microscopy (XTEM) and X-ray double crystal diffractometry (DCD).