The follow-up sera from 33 patients who received allogenic bone marrow transplantation (BMT) were tested by ELISA for antibodies to liver derived antigens present in a macromolecular, lipid associated, protein complex (LSP). Anti-LSP were found in 20% of patients with graft-vs-host disease (1 with acute GVHD, 3 with chronic GVHD), but in none of the 13 patients without GVHD. Lymphocytotoxic antibodies (LCTA) were frequently detected with similar prevalence in patients with and without GVHD. In the 4 anti-LSP +ve cases, LCTA serum levels did not follow the trend of anti-LSP antibody levels. Liver biopsy was performed in 10 patients with clinical and biochemical sign of GVHD and showed features of hepatic GVHD in six cases; although piecemeal necrosis was present in 3 cases, anti-LSP were detected only in one patient. An anti-LSP response can be elicited in patients after BMT only during GVHD, with no relationship to LCTA and without a close association with signs of periportal hepatocyte damage.