Background: * Chronic graft-versus-host disease (cGVHD) is a multi-organ alloimmune and autoimmune disorder that occurs following allogeneic hematopoietic stem cell transplantation (alloHSCT). It is characterized by immune dysregulation, immunodeficiency, impaired organ function, and decreased survival. * Each year about 8000 patients receive allogeneic hematopoietic stem cell transplant (alloHSCT) in North America and about 50% of patients who are transplanted develop cGVHD. * Chronic GVHD is also a disorder that simultaneously affects many organ systems in highly variable fashion and requires complex and coordinated medical management by multiple medical specialties. There is an urgent need for progress in understanding and effective treatments for cGVHD as it is one of the most serious complications of cancer therapy and hematopoietic stem cell transplantation.

Objectives: * To establish a multidisciplinary clinic infrastructure for study of the pathogenesis and natural history of cGVHD. * To prospectively identify clinical and biological prognostic markers in patients with cGVHD * To develop clinically relevant cGVHD grading scales * To identify novel biological characteristics of cGVHD and to describe them in the context of clinical history and presentation * To identify potential clinical and biological markers of cGVHD activity * To improve understanding of the biology of cGVHD-associated graft-versus-tumor effects * To identify potential patients for cGVHD treatment protocols at the NCI and NIH

Eligibility: -Patients age 1 and older referred by the primary transplant physician for the evaluation of chronic graft-versus-host disease independent of underlying diagnosis.

Design: * Patient undergoes initial clinical and laboratory multispecialty work-up at the NCI cGVHD clinic. * Minimally invasive biopsies and rarely, deep tissue biopsy may be obtained to confirm the diagnosis and/or rule-out other pathologic process (in adults only). * Long tem data collection for evaluation of long-term outcomes will be conducted anually as feasible