Two cases of choroid plexus cysts detected antenatally with ultrasonography are described. The first case involved an 18-week fetus with a 10 mm unilateral bilocular anechoic mass in the glomus of the choroid plexus. This mass resolved by ultrasonic examination at 23 weeks gestation. The second case presented at 21 weeks gestation with a unilateral anechoic mass in the choroid glomus of the left lateral ventricle. A 410 g female still-born was delivered 2 days following the initial examination. Histopathologic examination of the fetus revealed an 8 mm ependymal cyst. The significance of choroid plexus cysts is poorly understood. Some researchers have reported these cysts to be entirely benign while others report an association with chromosome defects. Review of the current literature revealed a 9.5% incidence of chromosome defects in fetuses with choroid plexus cysts.