Auger electron spectroscopy technique was used to study surface segregation of Ge in concentrated amorphous Si1-xGex thin film alloys. The alloys (with Ge bulk concentrations in the range of 18-58 at.%) were prepared by dc magnetron sputtering and annealed in a UHV chamber in the temperature range of 653-673 K. The surface equilibrium data (X-s(Ge) versus X-b(Ge)) were determined from segregation kinetics. We show that (i) the experimental data can be interpreted using McLean-Langmuir isotherms with a segregation enthalpy DeltaH((exp)) equals to 5.3 +/- 0.5 kJ mol(-1) and (ii) the estimated segregation enthalpy is lower than the theoretical one calculated in crystalline alloys neglecting the alloying and the size effects. (C) 2003 Elsevier Science B.V. All rights reserved.