Adrenocortical sarcoma is an extremly rare tumour associated with a quite pejorative evolution.We report the case of a fifty-eight years old woman presenting a chronic asthenia and acute flank pain. She had no hypertension, no clinical sign of virilization or hypercorticism. Abdominal ultrasonography revealed an 8 centimeters mass above the right kidney. CT scan aspect evoked an adrenal carcinoma embolizing vena cava. Hormonal assays did not reveale any inappropriate secretion (17 alpha hydroxyprogesterone, 11 desoxy-cortisol, cortisol, dehydroepiandrosterone-sulfate, delta-4 androstenedione, testosterone, aldosterone, renin, 24-hour urine metanephrine and normetanephrine). A radical adrenalectomy associated with a nephrectomy was performed. Tumour measured 13×7.5×5 centimeters, weighed 760 grams. Histological study confirmed the diagnosis of adrenal carcinoma, but described a sarcomatous component occupying nearly twenty percent of the total mass. Immunohistochimical labelling was positive for anti-vimentin, anti-desmin and anti-actin antibodies. In addition to surgical resection, the patient received mitotane as adjuvant treatment (6 g per day, mitotanaemia: 20.6 mg/l). After a 16 month evolution, physical exmination, CT scan, PET scan and hormonal monitoring dont show any evidence of local reccurence or metastasis. In the last twenty years, only four cases of adrenocortical carcinosarcoma have been reported in literature. One was a non secreting tumor, the three others were revealed by aldosterone, androgen or catecholamine secretion. Considering pathology, one had an osteogenic and chondroid differenciation, the two others a rhabdomyosarcomatous differenciation. To our knowledge, this is the first observation of an adrenal carcinosarcoma expressing a smooth muscle phenotype. The strikingly good evolution in our patient is also particularly unusual. Indeed adrenocortical sarcoma is a cancer with a very poor prognosis since in all other cases, life expectancy after diagnosis has never exceeded 8 months.