Abstract: Molecularly imprinted polymers have been synthesized using 17 alpha-ethynylestradiol as template. The affinity and the specificity of the polymers towards the template were evaluated by radioligand immunoassay. The polymer prepared in toluene with 4-vinylpyridine as functional monomer and ethyleneglycol dimethacrylate as crosslinker was found to have a strong and highly selective affinity for 17 alpha-ethynylestradiol. A comparison with the natural antibody indicated that the recognition properties of the polymer towards several structurally related steroids were similar or superior to those of the antibody. The results show that it is possible to make a successful polymeric receptor site for a lipophilic molecule that can provide only two potential points of hydrogen bonding interaction