We describe massive enlargement of both adrenal glands in 3 newborns, 2 girls and 1 boy. Two had hemihypertrophy and other congenital abnormalities but no identified genetic mutation; the third had genetically proven Beckwith-Wiedemann syndrome. Two had severe Cushing syndrome, the third had hypercortisolemia but no clinical Cushing syndrome. Bilateral adrenalectomy cured Cushing syndrome in the 2 with the severe symptoms; total adrenal weight was 44 and 53 gm in the patients, respectively. Unilateral adrenalectomy was performed in the third patient: the gland weighed 52 g; postoperatively, the patient's hypercortisolemia normalized and, concomitantly, the enlarged contralateral adrenal gland had a 5-fold decrease in size to slight enlargement 6 years postoperatively. Microscopically, the 3 patients had similar pathology: massive adrenal enlargement due to a combination of cytomegaly, persistence of the transient cortex, and hyperplasia of the permanent cortex. The pathological findings were most likely the result of the genetic mutation identified in 1 patient and of an unknown mutation in the remaining 2 patients.