Mandibular hypoplasia is a frequently encountered craniofacial difference and can be classified into three groups: congenital, developmental, and acquired. The focus of this article is on the congenital group, the majority of which is associated with syndromes. There have been numerous publications on patients with syndromic congenital mandibular hypoplasia; however, there has been no investigation and differentiation of the "nonsyndromic" patients. The purpose of this study was to analyze this subgroup of patients with nonsyndromic congenital mandibular hypoplasia to determine incidence, clinical presentation, and treatment.A retrospective analysis of all children treated for congenital mandibular hypoplasia at the Children's Hospital of Philadelphia between 1975 and 2003 was performed. Two hundred sixty-six patients were identified during this 27-year period. Of these 266 patients, 148 presented with oculo-auriculo-vertebral (OAV) spectrum, 52 with mandibulofacial dysostosis, 31 with Pierre Robin sequence, and 17 with miscellaneous syndromes. The remaining 18 patients were identified as having congenital mandibular hypoplasia without any known syndrome. Of the 18 patients with nonsyndromic congenital mandibular hypoplasia, 17 had primary bilateral growth anomalies and 1 had a primary unilateral growth disturbance resulting in bilateral deformity. Seven patients were products of a complicated pregnancy, 10 patients required tracheotomy or prolonged intubations, and 7 required gastric tube feedings. Associated anomalies included temporomandibular joint ankylosis in five patients, aglossia/microglossia in three patients, and rare craniofacial clefts in three patients. The average number of procedures required to treat the mandibular deformity for each patient was six. Although mandibular hypoplasia is a common craniofacial anomaly, patients manifesting nonsyndromic congenital mandibular hypoplasia are a rare subgroup. Case reports illustrating the range of mandibular deformities are presented.