Tow of three patients seen with malignant tumor of adrenals had very large lesions and the outcome was rapidly fatal. Excision of tumor was possible in the third case and the patient is in good health two years after operation. Clinical signs are infrequent and diagnosis of an adrenal lesion is mainly dependent on combined ultrasound-scan imaging, with confirmation by histology. Differential diagnosis is necessary between adrenal cortex adenoma and pheochromocytoma. Malignancy is suspected from signs of extratumoral invasion and a tumor weight of over 100 g. Histologic findings are not always specific. Treatment is almost exclusively surgical, complementary therapy being unnecessary in non-secreting pheochromocytoma. Attempts to treat malignant adrenal cortex masses by o,p-DDD have not improved prognosis. The chance discovery of a small tumor requires either routine excision of mass to prevent progression of certain malignant tumors, or simple surveillance, particularly after 50 years of age, since many of these tumors are benign: the decision for choice of therapy is a debatable subject.