Kinetic aspects of the transformation of poly(tetrafluoroethylene) (PTFE) from phase IV to phase II at 19 degrees C and atmospheric pressure were studied using wide angle X-ray diffraction (WAXD) following a rapid decrease in temperature from 24.7 to 14.5 degrees C. Information relating to changes in molecular packing was obtained from the position of an equatorial peak. Changes in the amount of disorder present were characterized by measuring the integrated intensity of peaks on the second layer line. Within the limits of error, the molecular packing and disorder changes occurred simultaneously as the transformation occurred. The kinetics of the transformation were evaluated following the approach of Avrami. The results indicate one-dimensional crystal growth in agreement with theory. The results from this study are discussed with respect to implications for the transformation mechanisms and previous work in this area.