Therapeutic dilemmas associated with antenatally detected ovarian cysts. Fifteen instances of ovarian cysts detected antenatally are reported. Seven cysts more than 5 centimeters in diameter were treated surgically because of clinical signs, such as palpable abdominal mass, vomiting and abdominal distension. Seven cysts less than 5 centimeters in diameter, and one cyst more than 5 centimeters in diameter began to regress spontaneously within six months after birth. Because the pathophysiologic nature of neonatal ovarian cysts has not been elucidated and because the borderline between physiologic and pathologic factors is still unclear, we propose a more conservative approach in the management of neonatal ovarian cysts to avoid unnecessary operations. 