The axial and transverse Young's modulus and thermal conductivity of gel and single crystal mat polyethylene with draw ratios lambda = 1-350 have been measured from 160 to 360 K. The axial Young's modulus increases sharply with increasing lambda, whereas the transverse modulus shows a slight decrease. The thermal conductivity exhibits a similar behavior. At lambda = 350, the axial Young's modulus and thermal conductivity are, respectively, 20% and three times higher than those of steel. For this ultradrawn material both the magnitude and the temperature dependence of the axial Young's modulus are close to those of polyethylene crystal. The high values of the axial Young's modulus and thermal conductivity arise from the presence of a large percentage (similar to 85%) of long needle crystals.