Ovarian cysts are common incidental findings in term infants and, if unusually large, may result in dystocia, torsion, or rupture. Torsion and infarction of a normal ovary tend to occur in older childhood. During a 4-month period, 3 cases of neonatal ovarian torsion were observed after antenatal ultrasonography had detected fetal pelvico-abdominal cystic lesions. The three infants were explored between 4 and 16 days of age. Ovarian torsion was right-sided in all 3, and 1 ovary had been autoamputated. The resected specimens were nontense, thin-walled cysts, filled with hemorrhagic fluid, that measured between 4.5 and 8 cm in diameter. Microscopically, focal calcification and widespread necrosis precluded recognition of underlying histologic landmarks. Neonatal ovarian cysts or cystic ovaries greater than 4 cm in diameter should be excised, even if asymptomatic, because they are prone to, or have undergone, torsion.