The paper presents experimental results that concern cold longitudinal rolling of flat bars made from EN AW-6063 aluminium alloy. The investigations aimed at determining the impact of the degree of deformation of material on the forward slip. The forward slips were calculated from Fink' s, Drezden' s and Vinogradov' s formulae. On the basis of investigations of the cold longitudinal rolling of flat bars made from aluminium EN AW-6063, it was found that the forward slip increases with an increase in degree of deformation of material.