The purpose of the present study was to investigate the cranial base on profile radiographs of patients with cri-du-chat syndrome and to relate the findings to current knowledge of brain malformation in an attempt to localize the developmental field affected in cri-du-chat syndrome. The material of profile radiographs of 23 patients was collected in Denmark in the 1970s. Twenty-two patients had terminal deletions of chromosome 5 (5p13.3, 5p14.1, 5p14.2, and 5p14.3), and one patient had an interstitial deletion. The cranial base angle (n-s-ba) was in most cases reduced and in no cases increased compared to age-related standards for normal individuals. Malformations in the bony contours of the sella turcica and the clivus occurred in cri-du-chat patients with terminal deletions. This specific cranial base region develops around the notochord at the location from where the rhombencephalic-derived brainstem, pons, and cerebellum have developed dorsally, and from where the neurons to the larynx have migrated ventrally. As the cranial base, the cerebellum and the larynx are involved in cri-du-chat syndrome, and attention is drawn to a new developmental field which comprises the dorsum sellae, clivus, cerebellum, and larynx. This field seemingly originates from the same notochordal location. The study has demonstrated a cranial base malformation in cri-du-chat patients, which ought to be elucidated in future research and combined with neurological and chromosomal investigations.