The morphology and crystal growth kinetics of isotactic polybutene-1 (PB1) trigonal phase in molten thin films were studied using transmission electron microscopy, electron diffraction and optical microscopy. The growth rate of the trigonal crystals, determined by in-situ optical microscopy, was one hundredth that of PB1 tetragonal crystals at about 75 degrees C. The growth rates of both trigonal and tetragonal crystals show the dependence on supercooling predicted by the nucleation theory. Trigonal crystals grown at 75 and 90.1 degrees C possessed well-faceted morphology, which suggests the existence of the flat growth faces between those temperatures that are required by nucleation theory. This is consistent with the observed temperature dependence of trigonal crystal growth rate in accordance with the nucleation theory. (C) 2008 Elsevier B.V. All rights reserved.