Objectives: To determine syndrome-specific type, severity, and prevalence of hearing loss to facilitate follow-up and treatment. Design: Tertiary pediatric hospital craniofacial clinic survey study. If insufficient or no data were available for a child, he or she was referred to an audiologist for puretone audiometry. Setting: Academic research facility. Patients: Information was gathered regarding 132 children and young adults with craniosynostosis. Main Outcome Measures: The primary outcome was hearing assessment of children and young adults with various types of craniosynostosis. A secondary outcome was inference regarding the incidence of otitis media among children and young adults with craniosynostosis. Results: We found mild or moderate hearing loss in 44.0% of patients with Apert syndrome, in 28.5% with Crouzon syndrome, in 62.1% with Muenke syndrome, in 28.6% with Saethre-Chotzen syndrome, and in 6.7% with complex craniosynostosis. Hearing loss was conductive in most patients with Apert, Crouzon, and SaethreChotzen syndromes and it was predominantly sensorineural in patients with Muenke syndrome. Sensorineural hearing loss at lower frequencies was found only in patients with Muenke syndrome. Conclusions: Most patients with syndromic and complex craniosynostosis have recurrent otitis media with effusion, causing episodes of conductive hearing loss throughout their lives. Sensorineural hearing loss can occur in all 4 syndromes studied but is the primary cause of hearing loss in children and young adults with Muenke syndrome. For patients with these syndromes, we recommend routine visits to the general practitioner or otolaryngologist, depending on national standards of care, to screen for otitis media with effusion throughout life. We also advise early screening for sensorineural hearing loss among children and young adults with these syndromes.