The confluence of molecular biology and clinical medicine has provided new and valuable insights in PBC. Our understanding of the immunobiology of PBC has changed dramatically using this new technology. It is now possible to explicitly define mitochondrial autoantigens and examine recognition sites, by using autoantibodies, at the primary sequence level. In addition, cloned antigens have been developed to reliably assay for presence of autoantibodies; the use of cloned recombinant antigens should replace that of traditional immunofluorescence for AMA assay. It is also now possible to begin the task of defining the role of T cells in the immunopathology of PBC and exploring the issue of whether immunotherapy is possible. Finally, there is increasing evidence that PDC-E2 is located on the cell membrane of biliary epithelial cells. The mechanism for this expression remains to be studied. The explosion of data in PBC is an example of the serendipity and synergy brought about by application of new techniques to investigate old problems.