Nylon 6 filaments were drawn under high pressure. By means of wide-angle x-ray diffraction and differential scanning calorimetry, nylon 6 fibers were investigated after drawing at 80° C to a draw ratio of 3.75 and pressure in the range of atmospheric up to 2000 kg/cm2It was found that by increasing the pressure, structural conversion from the γ-pseudohexagonal to the α-monoclinic form occurs, and that crystallinity and orientation are also increased.