Crown ethers are a unique category of ionic complexants whose recognition properties derive from both the atoms within the molecule and the overall structure. Immobilization of the crown ethers onto polymers allows for ease of handling, recyclability and adaption to continuous processes for this important set of complexants. The purpose of this review is to examine the different immobilization schemes for crown ethers having varying sets of donor atoms on organic polymers and the resulting metal ion affinities in order to provide an understanding of the strategies which are available to the synthesis chemist. The syntheses may be divided into three categories: (1) step-growth polymerization, (2) chain-growth polymerization, and (3) post-functionalization of pre-formed polymers. It is found that apparent metal ion affinities may be influenced by accessibility of the ions into the matrix. Use of hydrophilic polymers can be important for a high degree of ionic complexation. (C) 2004 Published by Elsevier B.V.