Ectopic ACTH secretion is a rare cause of hypercortisolism. Induced metabolic disturbances are often serious, and the management of such patients may be difficult. We report here our experience with four medullary thyroid carcinoma (MTC) patients with distant metastases in whom an ectopic ACTH syndrome occurred. The clinical presentation was significant by the severity and the rapidity of the hypercortisolism. Diagnosis and follow-up were realized by measurements of plasma cortisol, urinary free cortisol, urinary 17-hydroxycorticosteroid, plasma ACTH, plasma LPH, serum calcitonin and carcino-embryonic antigen. Initial treatment with adrenalytic medical therapy failed to control the disease. Only bilateral adrenalectomy cured the excessive cortisol production, and for a long time despite tumor progression. In conclusion, bilateral adrenalectomy should be considered in MTC patients with Cushing's syndrome even at the stage of distant spread. In fact, with regard to the slow growth rate of most MTC's, they may survive for years.