AbstractIn a study of 100 cerebellums from children dying with meningomyelocele, the lobular pattern of the dislocated segment was identified and classified. There was a graded variation in the degree of cerebellar deformity ranging from complete absence of cerebellar tissue in the upper cervical canal to one in which the upper cerebellar lobules were displaced through the foramen magnum. Within this range there were 2 instances in which the cerebellar defect conformed to that found in the Chiari type 1 deformity, consisting of prolapse of tonsillar tissue only. During fetal life the lobular relation in the caudal aspect of the cerebellum undergoes considerable change and it is likely that the type of deformity present in the cervical canal is closely related to the stage of cerebellar development at which the alteration in growth has its inception. The evidence presented argues against the defect being of a primary developmental nature. The terms “Chiari type 1 deformity” and “Arnold‐Chiari malformation” have outlived their usefulness and future descriptions of the cerebellum in children with hindbrain deformities should indicate the shape of the lobules and precise ones involved in the h