The phase equilibria in the Fe-Nb-Ti ternary system at 1000 degrees C, 1100 degrees C and 1200 degrees C have been experimentally investigated on ternary equilibrated alloys by means of optical microscopy (OM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The Fe-Ti binary system was reassessed and the Fe-Nb-Ti ternary system was thermodynamically optimized using the CALPHAD (Calculation of Phase Diagrams) method. The obtained self-consistent parameters describing the Gibbs energy of each phase in the Fe-Ti and Fe-Nb-Ti systems lead good agreement between the calculated results and most of experimental data. (C) 2011 Elsevier B.V. All rights reserved.