Graft coronary disease (GCD) has emerged as the most important deterrent to long-term survival in adult heart transplant recipients. The incidence, natural history, and pathobiology of GCD is less well understood in the pediatric transplant population. This study evaluated the histopathologic and immunohistochemical features of GCD in the Stanford pediatric heart and heart-lung group. Eighty-eight patients, ages 1 week to 18 years, received heart transplants between 1974 and 1992, and 15 patients, ages 1 month to 18 years received heart-lung transplants between 1981 and 1992 at Stanford University Hospital. There were 50 males and 38 females in the heart transplant group; 39 (11%) had idiopathic cardiomyopathy, 26 (30%) had congenital heart disease, 13 (15%) had viral cardiomyopathy, seven (8%) had familial cardiomyopathy, two (2%) had cardiomyopathy resulting from doxorubicin therapy, and one other case was not further delineated. In the heart-lung transplant group, there were eight males and seven females; pretransplantation diagnoses included nine (60%) with congenital heart disease and Eisenmenger's physiology, three (20%) with primary pulmonary hypertension, and one (7%) each with cystic fibrosis, bronchopulmonary dysplasia, and congenital lymphangiectasia. Fifteen (17%) of the heart transplant recipients and three (20%) of the heart-lung transplant recipients had GCD on angiographic or pathologic examination. Histopathologic samples were available on 14 cases (11 heart transplants and three heart-lung transplants).(ABSTRACT TRUNCATED AT 250 WORDS)