A complete thermodynamic investigation of the Ge-Ti system was performed in this study. Seven samples were prepared by arc-melting the pure elements in order to check the literature data on phase diagram and enthalpy of formation of Ti5Ge3. The samples were annealed at certain temperatures for extended periods of time, and then quenched. Both the as-cast and annealed samples were examined by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) technology. The phase transformation temperatures were measured by differential thermal analysis (DTA). The measurement on enthalpy of formation for Ti5Ge3 was performed using the Kleppa-type HTRC with the calorimeter temperature set at 1100 +/- 2 degrees C. Based upon the literature data and current experimental results, the Ge-Ti system was critically assessed by means of CALPHAD approach. The calculated phase diagram and thermodynamic properties agree well with the literature data and the present experimental results. (C) 2011 Elsevier B.V. All rights reserved.