A 73-year-old female was admitted to our hospital because of weight loss and pretibial edema. Plasma levels of adenocorticotropic hormone (ACTH) and cortisol were elevated, and neither hormone showed circadian rhythm. Dexamethasone (2 mg for 2 days) failed to reduce the urinary excretion of 17-hydroxycorticosteroids and the plasma cortisol level. The stomach biopsy specimens showed a moderately-differentiated papillo-tubular adenocarcinoma. Computed tomography of the abdomen showed multiple metastases to the liver. Immunohistochemical staining of the autopsy specimens showed immunoreactive ACTH in the primary tumor cells of the stomach as well as the metastatic tumor cells of the liver. On the basis of the clinical, histological and immunohistochemical findings, we diagnosed this patient as having ectopic ACTH syndrome caused by adenocarcinoma of the stomach.