Functional polymeric materials with desired properties can be designed by precise control of macromolecular architectures. Over the recent years, click reactions have enabled efficient synthesis of a variety of polymers with different topologies via efficient polymer-polymer conjugations. While the copper catalyzed Huisgen type (3+2) dipolar cycloaddition between azide and alkyne has been widely used toward this goal, the Diels-Alder (DA) reaction offers an alternative click reaction that allow efficient macromolecular conjugations, oftentimes without the need of any additional reagent or catalyst. This article highlights, with illustrative examples, the power of the DA "click" reaction to efficiently synthesize a variety of different well-defined macromolecular constructs in a modular fashion. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4103-4120,2011