The mechanical behavior of oriented bars of polyethylene obtained by heavy rolling with side constraints was studied. The bars were rolled to a permanent deformation ratio (DR) of up to 8.3. The elastic modulus and ultimate strength measured along the rolling direction increase with increasing DR. For samples deformed to DR = 8.3, the ultimate strength exceeds 180 MPa, whereas an unoriented material exhibits a strength of merely 15 MPa. Because of the highly ordered lamellar structure of the rolled material, the tensile deformation of the bars along the rolling direction is reversible to a large extent. The oriented bars of polyethylene also demonstrate very high toughness, especially in the direction of side constraints. Izod impact tests revealed that the impact strength of the oriented bars exceeds 200 kJ/m(2). The samples did not fracture on impact and showed only limited delamination in planes parallel to the rolling plane. Most of the delivered energy was consumed during specimen bending rather than fracture. In contrast to the tensile properties, there is an optimum DR around 5, for which the impact strength is the highest. Dynamical mechanical measurements showed that heavy rolling to a high strain, above DR = 6, produces not only a well-developed orientation of the crystalline component but also high orientation and transverse ordering of the amorphous phase, which leads to the anisotropy of the material properties in the loading direction/constraint direction plane, perpendicular to the rolling direction.