To study clinical and placental associations of increased amount of chorionic disk extravillous trophoblast (IAEVT), the frequency of selected clinical and placental parameters of 189 consecutive cases with IAEVT, defined as more than 5 cell islands and/or placental septa per placental section, were compared with those for all remaining 1,006 placentas examined during the same period. IAEVT was statistically significantly associated with preeclampsia, decidual arteriolopathy, placental infarction, and several chronic placental hypoxic lesions (uterine hypoxic pattern of hypoxic placental injury, microscopic chorionic pseudocysts, massive perivillous fibrin deposition, and trophoblastic multinucleated giant cells in decidua) and absence of meconium staining and umbilical cord abnormalities. The amount of chorionic disk extravillous trophoblast is increased in association with clinical conditions and placental lesions associated with chronic hypoxia of uterine origin, ie, placental malperfusion. Counting placental septa and cell islands is a valuable surrogate test of chronic placental hypoxia.