The coarsening of co-continuous morphologies in polymer blends with annealing is studied, demonstrating the effect of interfacial tension, viscosity and also physical cross-links in blends with thermoplastic elastomers. Go-continuous morphologies of 50/50 wt% stay co-continuous with annealing but show a linear increase in phase size with time. The 30/70 wt% blends break up into droplet/matrix morphologies and shows an increase in phase size in the first stage of the coarsening process. A relation has been proposed, using only the interfacial tension and viscosities of both components, to predict the growth rate of coarsening. The relation shows good agreement with the rates found experimentally. The coarsening process in blends with thermoplastic elastomers is severely slowed down or even stopped when physical cross-links are present in the thermoplastic elastomers. The driving force for coarsening is too small to overcome the stabilizing force due to physical crosslinks. (C) 2000 Elsevier Science Ltd. All rights reserved.