Five infants had congenital unilateral microcoria. The red reflex was absent and vision was severely reduced in all five eyes preoperatively. A pupil was created surgically in three of the eyes, resulting in a variable improvement in vision. The underlying lens was clear in all three children. The origin of the pupillary anomaly is unknown, but probably is related to remnants of the fetal pupillary membrane. Early surgical treatment and vigorous occlusion therapy can result in useful vision.