Adrenocortical tumors are rare in children and present with variable signs depending on the type of hormone excess. We herein describe the unusual presentation of a child with adrenocortical tumor and introduce the concept of in vitro chemosensitivity testing. cAsE rEPOrt: A 10.5-year-old girl presented with hypertrichosis/hirsutism and weight loss. the weight loss and behavioral problems, associated with halted puberty and growth, led to the initial diagnosis of anorexia nervosa. However, subsequent weight gain but persisting arrest in growth and puberty and the appearance of central fat distribution prompted further evaluation. rEsULts AND FOLLOW-UP: 24h-urine free cortisol was elevated. Morning plasma ActH was undetectable, while cortisol was elevated and circadian rhythmicity was absent. thus a hormonally active adrenal cortical tumor (Act) was suspected. On magnetic resonance imaging (MrI) a unilateral, encapsulated tumor was found which was subsequently removed surgically. tissue was investigated histologically and for chemosensitivity in primary cell cultures. Although there were some risk factors for malignancy, the tumor was found to be a typical adenoma. Despite this histology, tumor cells survived in culture and were sensitive to cisplatin in combination with gemcitabine or paclitaxel. At surgery, the patient was started on hydrocortisone replacement which was unsuccessfully tapered over 3 months. Full recovery of the hypothalamus-pituitaryadrenal axis occurred only after 3 years. cONcLUsIONs: the diagnosis of a hormonally active adrenocortical tumor is often delayed because of atypical presentation. cortisol replacement following unilateral tumor excision is mandatory and may be required for months or years. Individualized chemosensitivity studies carried out on primary cultures established from the tumor tissue itself may provide a tool in evaluating the effectiveness of chemotherapeutic drugs in the event that the adrenocortical tumor may prove to be carcinoma.