Presentation of a 48-y old woman who developed a neuroendocrine tumor of the nasal cavities. This lesion progressed rapidly despite an extensive resection and repeated chemotherapy. The patient refused radiotherapy. Before her death, 28 months later, she exhibited a paraneoplastic Cushing-like syndrome. At autopsy, restricted to the brain, there was a 5 cm diameter tumor invading the frontal area without alteration of the hypothalamus or the pituitary gland. Routine histology and electron microscopy confirmed the neuroendocrine nature of the tumor. Immunohistochemistry revealed the tumor to be positive only for neurone specific enolase, negative for S-100 protein, neurofilament and ACTH. The pituitary gland was positive for most usual hormones (GH, PRL, TSH, LH, FSH) but only few cells were slightly positive for ACTH. Many Crooke cells were observed. These findings suggest that the tumor secreted an ACTH-like substance (not detected actually by immunochemistry) that stimulated the activity of the adrenal cortex but inhibited normal production of ACTH at the pituitary gland level.