This note is concerned about the circumstances, under which flow induced crystallization can take place. In first instance, a discrimination must be made between two temperature ranges. One of these ranges is between the equilibrium melting point of ideal crystals and the melting temperature of spherulitic structures. The other range is below the temperature, where spherulites melt. A second question is, whether one has to do with homogeneous (sporadic) nucleation or with heterogeneous nucleation on so-called defects. In other words, does flow actually cause sporadic nucleation in a homogeneous medium or does it merely activate kind of already existing dormant entities. A third point is the mechanism of the growth of nuclei. The applied specific work is of importance. (C) 2013 The Society of Rheology.