Six cases of chorioangioma of the placenta and a review of relevant literature are presented. The incidence of chorioangiomas is higher than generally realized because many small chorioangiomas are missed in routine examination of placentas. A case of chorioangioma with foci resembling hemangiopericytoma is presented. Cases of large chorioangiomas seem to occur when the placenta is large. Hydramnios is commonly found with large chorioangiomas, and both of these conditions may be conducive to premature births. There is an increased incidence of toxemia in pregnant patients with chorioangiomas, and the condition is unrelated to the size of the tumor. Diligent examination of infants associated with chorioangioma of the placenta is suggested, as these infants may have unsuspected congenital anomalies.