Two novel monoclonal antibodies, GE1 and GE2 raised against the C-terminal 31 and 28 amino acids of the estrogen-inducible trefoil peptide pS2, are described. Both antibodies are able to detect pS2 in formalin-fixed, paraffin-embedded tissues. Conditions are presented under which pS2 can be shown in cell lines by immunohistochemistry that has previously been problematic. The antibodies can specifically show the presence of pS2 in cell lysates by Western blotting and immunoprecipitation. In the form of an affinity column, the GE1 monoclonal antibody can be used to purify pS2 from MCF-7 supernatants. The eluted peptide from the GE1 affinity column shows a single band at 6,600 Da (predicted size for pS2) on Western blotting. These antibodies are valuable reagents in the analysis of the role of trefoil peptides in the maintenance of mucosal integrity, and may have applications in the assessment of pS2 expression in chronic gastrointestinal ulceration and adenocarcinomas that secrete pS2, where it may serve as a prognostic marker.