Chronic graft-versus-host disease can mimic various autoimmune disorders, although autoantibodies are rarely detected in the sera of affected patients. Antibodies to cytoskeleton are a frequent finding in patients affected by autoimmune disorders. In all the sera of 16 patients who were submitted to allogeneic bone marrow transplantation, we have found antibodies against cytoskeletal intermediate filaments. Moreover, the titer of such antibodies is quite elevated when compared with those reported in autoimmune disorders. A statistically significant difference between the titers found in patients without and with cGVHD (median 1:40 vs. 1:256, P less than 0.05) has been found. This would suggest that such antibodies might be relevant in monitoring clinical course. Furthermore, since certain cytoskeleton antigens have been shown to be expressed also on cell membrane, antibodies against intermediate filaments might also play a more important role by interfering with such surface structures.