The enthalpies of formation of Nb-Ru alloys in the whole range of composition and of two compositions in the Nb-Ru-Al ternary system corresponding to Nb(Ru,Al)(2) and NbRu2Al identified by Cerba et al. [P. Cerba, M. Vilasi, B. Malaman, J. Steinmetz, J. Alloys Compd. 201 (1993), 57-60], have been measured by high-temperature direct reaction synthesis calorimetry at 1775 K. For some binary alloys the experiment cannot provide results because the direct reaction synthesis is not completed contrarily to ternary alloys experiments. The results are compared with predicted ab initio data. (C) 2008 Elsevier B.V. All rights reserved.