AbstractThis paper presents a sonographic diagnosis of exencephaly made during the last trimester of gestation. The sonogram showed the absence of bones in the cranial vault together with the presence of a disorganized cerebral mass, with loss of its normal anatomy. Post‐partum examination of the newborn confirmed the findings of the sonogram. We briefly review the characteristics of exencephaly, its aetiology, and its relationship to anencephaly.