Toughness measurements of a Ti-45Al-2N4u-2Nb + 0.8%vol TiB2 alloy with a. near fully lamellar microstructure and a Ti-46Al-8Nb alloy with a convoluted microstructure are performed at 650 degrees C under vacuum according to ASTM Standard E1820. Respective values of K-Ic = 18 MPa root m and 20 MPa root m are found, with comparatively good repeatability the toughness of these two alloys is thus relatively similar, despite significant differences in miciostructure and crack path.