Tensile properties have been investigated at 1273-1973 in rolled and annealed pure W and W-La 2 O 3 sheets. The as-rolled W-La 2 O 3 exhibited higher strength than the annealed pure W. On the other hand, the annealed W-La 2 O 3 exhibited higher strength than the annealed pure W. The higher strength of the annealed W-La 2 O 3 is attributed not only to the dislocation-particle interaction but also to the substructure which is stabilized by the La 2 O 3 particles.