Amnion nodosum is commonly regarded as a placental hallmark of severe and prolonged oligohydramnios. It consists of nodules of amorphous granular material present on the surface of the amnion. We reviewed all 45 cases of amnion nodosum from our placental database from 1994 through 2003 (study group). The control group consisted of 45 cases from the same database matched for gestational age but without amnion nodosum. Oligohydramnios, multiple pregnancy, perinatal mortality, macerated stillbirths, and chronic twin-twin transfusion were the most common clinical features encountered in the study group. Luminal vascular abnormalities of chorionic villi, fibrosis of chorionic villi, and placental edema were the placental features that were more frequently present in the study group.