We report on a 50-year-old patient with a giant benign adenoma of the adrenal cortex, which ruptured spontaneously, leading to life-threatening retroperitoneal hemorrhage. Following emergency adrenalectomy with sparing of the ipsilateral kidney, an adenoma of the adrenal cortex with a diameter of 18 cm and a weight of 1400 g was found. A detailed literature search showed this to be the largest benign tumor of the adrenal cortex described so far. We discuss the diagnosis and treatment of this unusual tumor.