Pregnancy rarely occurs in women with Cushing's syndrome, and when it does, fetal mortality and morbidity are very high. We describe a 30-year-old woman who was found to have severe Cushing's syndrome in the 22nd week of her first pregnancy, after a year of unsuccessful attempts to conceive. The patient had the majority of the symptoms and signs characteristic of the syndrome. Laboratory examinations revealed hypokalemia of 2.7 mEq/l, serum cortisol 39.5 micrograms/dl without diurnal variation, free urinary cortisol 1,850 to 3,500 micrograms/24 h, 17-hydroxycorticosteroids (OHCS) 52.5 mg/24 h, 17-ketosteroids (KS) 12 mg/24 h, and ACTH 29 pg/ml. No suppression was observed upon dexamethasone administration (2 and 8 mg). Ultrasound examination of the adrenal glands revealed a left adrenal tumor with a diameter of 4.2 cm. An adrenocortical adenoma was successfully excised in the 24th week of pregnancy. During the 37th week of pregnancy, she delivered a normal baby girl. Postoperatively, the patient was put on maintenance therapy. One year after delivery, mother and child are in perfect health.