In the first part of this work, the β (or B2)-stabilizing effectiveness was discussed by experimentally determining the temperature dependence of equilibrium volume fraction of the β (or B2) phase as well as the variation of the β-transus temperature as a function of β-alloying additions. In the second part, the thermal stability of the B2 matrix in three intermetallic compounds (Ti₂AlNb, Ti₂AlMo and Ti₅Al₂V) was studied. Flow stress anomalies were observed in these alloys deformed in compression as the testing temperature was increased. The transition phases which appear in Ti₂AlNb and Ti₅Al₂V compounds over the 650–850 K temperature range are responsible for these anomalies. Implications of such B2 decompositions on the development of this category of alloys are briefly discussed.