Introduction: Untreated obstructive sleep apnea (OSA) has deleterious effects on one's overall health. Recent literature suggests that craniofacial abnormalities, as noted on a lateral cephalometric radiograph (ceph) or clinically by the presence of a posterior crossbite, may be associated with OSA. Literature also suggests that if abnormal ceph measurements are noted or if a patient presents with a posterior crossbite, then further questioning about that patients sleep habits and snoring should be addressed. The primary purpose of this study is to explore any possible associations between ceph measurements, and/or presence of a posterior crossbite with OSA, as determined by the Berlin sleep questionnaire, in the orthodontic population. The second purpose of this research is to outline a part 2 follow-up study through administration of an at home sleep test, the Nox-T3 sleep monitor, to further validate presence of OSA. The overall goal is to see if the combined data from the Berlin score, the clinical presence or absence of a posterior crossbite, and standard orthodontic ceph measurements can increase the predictive value of patients in the orthodontic office who might be suffering from obstructive sleep apnea. Methods: A total of 85 consecutive subjects who were already undergoing records in 5 private practice orthodontic offices around the greater Philadelphia area were recruited for voluntary participation in the study. A Berlin questionnaire, lateral ceph, and any noted presence of a posterior crossbite were collected on all subjects. 12 ceph measurements (SNA, SNB, ANB, Co-A, Co-Gn, A-Na perp, Pg-Na perp, SN-MP, FH-MP, Ba-SN, Wits, and MP-Hyoid) were traced by a second year orthodontic resident. 5 subjects were then selected using a random numbers table and given the Nox-T3 sleep monitor for self-administration to record their sleep for one night. Statistical analyses were run using SAS version 9.2 to evaluate any associations. Results: A total of 76 subjects completed data collection, whereas 9 subjects either failed to report their height, and/or weight, and/or failed to complete the Berlin questionnaire in its entirety thus excluding them from the study. A total of 11, or 14% of subjects scored high on the Berlin, meaning a high risk of suffering from OSA. Of all ceph measurements, the only one that showed a statistically significant association with the high Berlin score was MP-Hyoid (p=0.0033). BMI alone was not found to be associated with the Berlin score (p=0.3712). Presence of a posterior crossbite also did not show any correlation with the Berlin score (p= 0.1000). Conclusions: 1) BMI was not found to be associated with the Berlin score among the orthodontic subject population. 2) MP-hyoid was found to be associated with the Berlin score, at a high level of statistical significance. 3) All other cephalometric measurements, including SNA, SNB, ANB, Co-A, Co-Gn, A-Na perp, Pg-Na perp, SN-MP, FH-MP, Ba-SN, and Wits, failed to show any statistically significant correlation to the Berlin score. 4) Posterior crossbite was not found to be associated with the Berlin Score among the orthodontic subject population. Key words: Obstructive sleep apnea, Berlin sleep questionnaire, cephalometric, posterior crossbite, Nox-T3 sleep monitor, orthodontic population / Oral Biology