An equiatomic high-entropy alloy CrMnFeCoNi has been severely deformed by high pressure torsion at room and liquid nitrogen temperature. The microstructure and texture has been analyzed by X-ray diffraction (X-ray line profile analysis and X-ray microdiffraction, respectively). It is shown that at a certain shear strain a steady state domain/grain size in the nanometer range and a dislocation density of the order of 1016 m-2 is reached, while the twin density goes over a maximum at this strain. The texture developed is typical for sheared face-centred cubic metals with a weak brass-type shear component dominating. Moreover, microhardness tests have been applied. Analysis of the strength suggests a Taylor-type hardening. The results will be discussed with regard to the mechanisms of deformation, including dislocation slip, twinning, martensitic transformation and grain boundary sliding.