Uniaxially and biaxially oriented samples of polyethylene irradiated by &ggr; rays have been investigated at room temperature. Both the tensile strength and the modulus of elasticity are found to increase as the degree of orientation induced by homogeneous deformation increases. But the tensile strength decreases as the dose of &ggr; irradiation increases while the modulus of elasticity increases. The combined effects seem to indicate that the &ggr; irradiation essentially destroys the macromolecular orientation and thus reduces the tensile strength to that of unoriented solid, but with relatively higher elastic modulus as a result of the occurrence of crosslinking.