Abstract: A molecularly imprinted uniform-sized polymer-based stationary phase for (S)-naproxen has been prepared by a multi-step swelling and thermal or redox polymerization method using 4-vinylpyridine and ethylenedimethacrylate as a host functional monomer and cross-linker, respectively. The obtained molecularly imprinted polymers were evaluated using aqueous-rich mobile phases. The molecularly imprinted polymer materials could separate naproxen enantiomers. Further, the materials showed high selectivity for naproxen and moderate selectivity for other 2-arylpropionic acid derivatives. On the other hand, the molecularly imprinted polymer materials showed little selectivity for other acidic compounds, and basic and neutral compounds. With regard to comparison of the molecularly imprinted polymers prepared by thermal and redox polymerization techniques, the latter materials gave higher retentivity and enantioselectivity than the former materials, while the former materials gave higher column efficiency than the latter materials. Thus, naproxen enantiomers were resolved much better on the molecularly imprinted polymer material prepared by a thermal polymerization method. (C) 1998 Elsevier Science B.V. All rights reserved