When graft-versus-host (GVH) disease affects the liver, it is characteristically the bile ducts which are involved, infiltrated by lymphocytes. To characterize this process further, and to determine whether there were any antigenic changes in the bile ducts, we stained 9 liver biopsies involved by GVH disease, 10 non-GVH biopsies that had a prominent portal lymphocytic component, and 8 biopsies taken incidentally at surgery for noninflammatory liver disease with epithelial membrane antigen, AE-3, AE-1, a keratin cocktail, keratin 19, CD45RO (UCHL-1), CD43 (Leu-22), CD20 (L26), vimentin, and LN-3. The infiltrating lymphocytes were T cells (CD45RO+, CD43+, CD20-) which variably expressed LN-3. The bile ducts were positive for the keratin cocktail, AE-1, AE-3, and keratin-19, but only occasionally positive for EMA and LN-3. There was no significant difference in the staining patterns of either the bile duct cells or lymphocytes between the three groups. With the antibodies that we used, there does not appear to be a significant difference in the antigenic phenotype of the bile ducts in GVH as compared to normal or reactive livers.