This paper is based on a presentation given at the de Gennes discussion meeting held at Chamonix in February 2009. The paper gives a personal review of the way developments relating to the stretching of polymer chains has taken place over the last 40 years. de Gennes was very influential in relation to chain dynamics concepts at the University of Bristol, where many pioneering concepts relating to chain stretching were developed by the late Sir Charles Frank and Andrew Keller. The paper reviews basic concepts on extensional rheology, droplet deformation, chain extension from extensional flow and the achievement of high chain extension for high-modulus polyethylene. The paper also reviews recent developments concerning the influence of chain stretching on polymer melt processing.