Martensitic β→α′(α″) and β→ω transformation in a series of Ti-base alloys with transition metals of groups IV-VIII have been investigated using the techniques of X-ray diffraction, optical and transmission electron microscopy. Phase and structural information is given on the non-equilibrium and metastable modifications occurring in these alloys during quenching from high-temperature β-field and aging. The conditions of the orthorhombic ″-phase, ω-phase and metastable β-phase formation in binary titanium-base alloys with