Single crystals of low M-w poly(4-methyl-1-pentene) (P4MP1) in its form 1 display an unusual streaking of their diffraction pattern. The crystals also frequently give rise to composite diffraction patterns made of two patterns rotated by 37 degrees. The streaking indicates a structural disorder, namely a shift of nearby layers along the a or b axis by one quarter of the unit-cell edge. The daughter crystals, rotated by 37 degrees, are produced on the edges of the parent crystals via an epitaxial growth that is a direct consequence of the structural disorder. (c) 2005 Published by Elsevier Ltd.