The mechanical relaxation behaviour of high and linear low density polyethylenes has been examined using tensile dynamic mechanical measurements and compared to the deformation behaviour observed in tensile drawing. In this way the relationship between the mechanical relaxations and the tensile deformation has been investigated. It is shown that the brittle-ductile transition relates to the gamma-relaxation while the yield behaviour is related to the interlamellar shear process and the c-shear process.