The fatigue strength of the material depends on a large number of parameters, in particular on the surface integrity. In the present work, specimens of Ti–6Al–4V titanium alloy after machining were investigated. The distribution of dislocation density and residual stresses was estimated by X-ray analysis. The results showed that the depth of plastically deformed layer increased from about 30 μm for a new tool to about 40 μm for a worn tool. It was found that the compressive residual stress at the surface is –190 MPa and the highest value is –220 MPa in subsurface of specimen machined by a worn tool. This distribution of residual stresses, which increases to a peak value from surface to some depth and then decreases, complies with the characteristic curve of residual stress field.