The tensile stress and Young's modulus of a series of gel-spun polyethylene fibers were measured in parallel to measurements of transverse and longitudinal sizes of crystallites, molecular orientation and straight-chain-segment (SCS) length distribution in order to find the correlation of the mechanical and microstructural characteristics during drawing. The low-frequency-Raman data evidence the predominance of the chain-straining process on the ends of crystallites. As a result, there appears a rigid intermediate substance (rigid amorphous phase (RAP)) between crystal cores and true amorphous phase. The RAP is composed of various-lengths SCS oriented in the fiber axis direction and arranged without longitudinal ordering. The RAP transforms gradually to uniform-length taut-tie molecules (TTM). The Young's modulus correlates to the increase of the RAP in length, but there were no detectable response of the mechanical parameters to the formation of the TTM. (C) 2003 Published by Elsevier Science Ltd.