• Procedures were carried out in a 12-year-old girl to relate Ewing's sarcoma of the left tibia with Cushing's syndrome. Computed tomography revealed a normal pituitary and hypothalamus but bilateral adrenal hyperplasia without focal enlargement, thus readily excluding hypothalamicpituitary-adrenal tumor. Negative results from a high-dose dexamethasone suppression test do not support pituitarydependent Cushing's disease. Ewing's sarcoma was diagnosed on tibial biopsy. The regression of the physical and biochemical findings of Cushing's syndrome subsequent to amputation of the left lower leg strongly suggests ectopic Cushing's syndrome caused by Ewing's sarcoma. Immunohistochemical studies of the resected bone were negative for corticotropin but positive for corticotropin releasing factor-like peptide. We conclude that this is the first reported case of ectopic Cushing's syndrome in a child that is caused by Ewing's sarcoma secreting corticotropin releasing factor-like peptide.