The tensile properties of three grades of linear polyethylene were enhanced by a factor of as much as 15 using a melt/solid phase compressive deformation process that produced equi-biaxial planar orientation in the sheet. Ultra high molecular weight polyethylene wi th planar isotropy and an in plane modulus of 10 GPa and a tensile strength of 330 MPa was produced using this method. It was found that the molecular weight had a significant influence on the optimum processing temperature, the ultimate biaxial deformation ratio and hence the ultimate tensile properties. High density polyethylene processed under ideal conditions had a tensile modulus of 2.3 GPa and a tensile strength of 250 MPa. The tensile strength increased linearly with increasing biaxial deformation ratio and the tensile modulus increased non-linearly with increasing biaxial deformation ratio. The deformation rate and the dwell time did not have a significant effect on the tensile properties. Shrinkage tests showed that biaxial deformation was less effective than uniaxial deformation in inducing orientation of the polymer chains, however differential scanning calorimetry results were consistent with the presence of extended chain crystals in very highly oriented ultra high molecular weight polyethylene sheets.