An organic chemical reaction where one of the species, for example, the substrate, the reagent, or a catalyst, is bound to a cross-linked, and therefore insoluble, polymer support. A major attraction of polymer-supported reactions is that at the end of the reaction period the polymer-supported species can be separated cleanly and easily, usually by filtration, from the soluble species. This easy separation can greatly simplify product isolation procedures, and it may even allow the polymer-supported reactions to be automated. Often it is possible to reuse or recycle polymer-supported reactants. Partly for this reason and partly because they are insoluble, involatile, easily handled, and easily recovered, polymer-supported reactants are also attractive from an environmental point of view.