An equiatomic high-entropy alloy CrMnFeCoNi was severely deformed at room temperature by high pressure torsion up to shear strains of about 170. Its microstructure and texture were analyzed by X-ray diffraction (X-ray line profile analysis and X-ray microdiffraction, respectively). It is shown that at a shear strain of about 20 a steady state domain/grain size of 24 nm and a dislocation density of 3 × 1016 m−2 is reached, while the twin density goes over a maximum of 2% at this strain. The texture developed is typical for sheared face-centred cubic metals, but it is extremely weak. The results are discussed in terms of the mechanisms of deformation, including dislocation slip, twinning and grain boundary sliding.