Over a period of 5 years, 25 children between 1 day and 26 months of age were prospectively evaluated because of the presence of meningomyeloceles. Cranial sonography was used to ascertain the types of associated cranial alterations. Twenty-three children (92%) presented signs of Chiari II malformation. In only two (8%) were the ultra-sonographic results normal. The abnormalities detected were classified as alterations of the ventricular system, extraventricular alterations, and associated findings. The most frequent alteration of the ventricular system was the "bat-wing" configuration of the frontal horns, which appeared in 22 children (88%). Among the extraventricular alterations, 23 children (92%) had a downward displaced cerebellum, obliterated basal cisterns and low positioning of the tentorium cerebelli. Associated findings were a polymicrogyria in 1 case and intracranial hemorrhage in 2. The 23 children with Chiari II malformation were followed up clinically and sonographically. Our findings were similar to those of other published series. In spite of the introduction of magnetic resonance imaging, we consider cranial sonography to be an inexpensive and convenient method of evaluating the existence of Chiari II malformation in the child with meningomyelocele and of following up its evolution after shunt procedures.