This paper is concerned with reminiscences of 50 years of research with crystalline polymers. It begins with the early days and the establishment of the basic thermodynamics of fusion of semi-crystalline polymers up to the present. In between are works involving crystallization kinetics, nucleation theory appropriate to polymers and the strong influence of molecular weight on the crystallization process and the resulting morphology, structure and properties. The problems and controversy regarding regularly folded chain and the crystallite interfacial structure, and their resolution was central to a great deal of activity during this time period. (c) 2005 Published by Elsevier B.V.