The tensile properties of β phase Ti–V, Ti–Mo and Ti–Nb polycrystals with various compositions were investigated at 300 and 77 K, and they were related to plastic deformation modes determined by optical and transmission electron microscopy. The stress-induced ω phase transformation occurs in {332}⟨113⟩ mechanical twins of the most unstable β Ti–V alloys with low vanadium content. Only slip operates in stable β Ti–V alloys with high vanadium content. {332}⟨113⟩ mechanical twinning not accompanied by the ω transformation appears in β Ti–V alloys with medium vanadium content. In Ti–Mo and Ti–Nb alloys {332}⟨113⟩ mechanical twinning and ⟨111⟩ slip occur depending on the alloy composition, while the stress-induced ω transformation does not appear. In all the alloy systems a high rate of work hardening and resultant large elongation to fracture are obtained by occurrence of stress-induced ω phase transformation and/or {332}⟨113⟩ mechanical twinning. The stable β titanium alloys deformed only by slip show high yield strength and small elongation.