The outer part of Hymenolepis diminuta tegument was extracted with 3 M KCl. The antigen was adsorbed from the extract on an affinity column containing H. diminuta-infected rat immunoglobulin immobilized on Sepharose 4B and could be eluted with 2.5 M urea at pH 2.8. Analysis of polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of both the crude extract and material eluted from the column showed that the latter was markedly purified. Double diffusion and immunoelectrophoresis revealed 11 and 4 antigenic components in the crude extract and purified preparation, respectively.