Abstract By in situ TEM deformation experiments, we studied in detail the deformation micromechanisms of a Ti–6Al–4V alloy at room temperature. All dislocations have an a-type Burgers vector and glide essentially in prismatic or basal planes. They are first emitted from α/β interfaces and take a preferential orientation along their screw direction. The motion of screw dislocations controls the strain rate. Our experiments allow the microscopic parameters of plasticity for this alloy to be determined for the first time. The results concerning the screw dislocation motion, its core structure and the influence of interfaces are then discussed in comparison with previously published results.