 Chronic graft-versus-host disease GVHD is one of the most devastating long-term complications after infusion of allogeneic hematopoietic stem cells, and it remains one of the major barriers to successful transplantation. Relatively little progress has been made in understanding and improving treatments for chronic GVHD over the last 20 years, and the survival rate after diagnosis of chronic GVHD has barely improved despite advances in supportive care. The National Institutes of Health convened a Consensus Conference on this topic in June 2004 and recently published its recommendations on improving research methods in a series of six papers. 