In a 1993 study, Mølsted and colleagues found an increased width of the spheno-occipital synchondrosis in newborns with complete clefts of the lip, alveolus, and palate compared with newborns with incomplete clefts. As the spheno-occipital synchondrosis represents remnants of the early chondrocranium that later ossifies and incorporates in the cranial base, it is possible that an inborn alteration, such as a deviant growth of cartilage, or a delayed maturation in the early development of the cartilaginous cranial base, can affect not only the length and the width of the cranial base, but also the petrous portion of the temporal bone and the nasal septum, as these structures also have a cartilaginous origin. The purpose of the present study was to measure the cranial base width, including the width of the maxilla, and to measure the bilateral angulation of the petrous portion of the temporal bone and the sphenoid bone in 3-month-old children with complete clefts and in 3-month-old children with an incomplete cleft of the lip, and to compare the two groups. Fifty-two children with complete clefts (CLP) without associated malformations comprised the test group. Forty-eight children with a minor, incomplete cleft lip (CL) constituted the control group. The results of the comparison showed marked differences between the CLP and CL groups. In the CLP children, the cranial base width and the bilateral angulation of the sphenoid bone increased. An increased angulation was also seen between left and right sides of the pars petrosa. Furthermore, increased maxillary width was found.(ABSTRACT TRUNCATED AT 250 WORDS)