Self-compatibilization is a novel method for preparing compatibilized polymer blends via concentrated emulsion polymerization. In this method, two partially polymerized concentrated emulsions are mechanically mixed, and then they are subjected to complete polymerization. Some compatibilizers are generated at the interfaces between the two kinds of cells, which compatibilize the homopolymers generated simultaneously inside the cells. In particular, when a rigid polymer was blended in this manner with a flexible one, tough materials were obtained. This review describes various ways to generate such self-compatibilized materials. (C) 2001 John Wiley & Sons, Inc.