Abstract: A potential problem associated with molecularly imprinted polymer (MIP) sorbents is that of cross-reactivity. In this study three MIPs (imprinted with Boc-L-phenylalanine, Boc-L-alanine, Boc-L-glutamic acid) plus a non-imprinted control were prepared and examined for their ability to bind differentially the enantiomers of boc-protected phenylalanine in an effort to quantify cross-reactivity and to develop a predictive model. Batch rebinding studies showed a degree of predictability for a number of MIP-ligand pairs, but other combinations showed unexpectedly high levels of cross-reactivity. Despite the general acceptance of heterogeneity of MIP binding sites, many previous studies report linear Scatchard plots, which is indicative of binding site homogeneity. The data horn this study produced curves, dearly demonstrating heterogeneity, The theoretical and practical implications of this heterogeneity are discussed, Chirality 9:233-237, 1997. (C) 1997 Wiley-Liss, Inc