Graft-versus-host disease (GVHD) remains the greatest source of morbidity-mortality in allogenic transplant patients. Although in most cases the more easily obtainable clinical and laboratory test parameters suffice to confirm the diagnosis and establish the stage of the disease biopsies of the affected organ are sometimes needed. At present there is great Interest in the study of factors allowing a prognosis of the course and type of response to treatment in patients with CVHD. In this sense, It would be necessary to objectively Identify and validate biomarkers capable of predicting biological or pathological processes in patients with cVHD. To this effect we have performed serial analyses of skin tissue using peripheral blood and tissue biomarkers in a prospective observational study conducted in three transplant centers. The still preliminary results Indicate that certain histopathological findings classically attributed to CVHD ore also seen in patients not clinically affected by the disease--this probably being related to other physiopathological phenomena occurring during transplantation. The study of these findings, combined with biomarker analysis, will allow improved understanding of the underlying etiopathogenesis, as well as the definition of new diagnostic, prognostic and response-evaluating criteria.