Bilateral craniofacial microsomia causes obstructive sleep apnea (OSA). We hypothesize that unilateral craniofacial microsomia (UCFM) is an underappreciated cause of OSA. The records of all pediatric UCFM patients from 1990 to 2010 were reviewed; only complete records were included in the study. UCFM patients with OSA (apnea hypopnea index >1/hr) were compared to UCFM patients without OSA. Univariate and multivariate Fisher and χ(2) tests were performed. Of the 62 UCFM patients, 7 (11.3%) had OSA. All OSA patients had Pruzansky IIB or III mandibles. OSA patients presented with snoring (71.4%), failure to thrive (FTT) (57.1%), and chronic respiratory infections (42.8%). Snoring (P < 0.001), Goldenhar syndrome (P = 0.001), and FTT (P = 0.004) were significantly associated with OSA, but race, obesity, clefts, respiratory anomalies, adenotonsillar hypertrophy, and laterality were not. The prevalence of OSA in UCFM patients is up to 10 times greater than in the general population. Snoring, Goldenhar syndrome, and FTT are significantly associated with the presence of OSA.