[en] The phase composition, dislocation structure and morphology of carbide precipitates in the Nb-1%Zr-0.1%C alloy are investigated after long-term holding (5000 and 10000 hrs.) at 900 deg C. It is shown that the long-term holding at 900 deg C under loading or without it leads to the decrease in creep resistance, to coarsening of carbide particles and increase of the carbide phase content in comparison with the initial state. During the test of the alloy under loading the particles also coarsen, but their average size decreases due to large amounts of fine dispersion precipitates (the size up to 400 A) in the structure. The results of study of mechanical properties and structure indicate the changes in geometry of carbide particles and formation of carbide precipitates of M₆C type after 5000 and 10000 hrs. holdings