Obstructive Sleep Apnea(OSA) is a common chronic disorder that is characterized by repetitive partial or complete cessation of air flow, associated with oxyhemoglobin desaturation and increased effort to breath, poor sleep, daytime sleepiness, mood disturbances, and stress. Individuals with narrow airways and/or craniofacial anomalies may have increased risk of OSA. It is classified as central, obstructive & mixed types. Skeletal features include retrognathic mandible, narrow mandibular arch, maxillary and mandibular arch retrognathism , hyoid bone position etc.,. Diagnosis of snoring and sleep apnea requires various modalities such as acoustic reflection, fluoroscopy, nasopharyngoscopy, cephalometry and computed tomography. Based on diagnosis OSA can be managed by behavior modifications, medications, positive airway pressure therapy, oral appliances like mandibular anterior positioners , tongue retaining devices, soft palate uvula lifting devices and surgical interventions. Thisbook gives an insight into the Obstructive sleep apnea, diagnosis and management in patients undergoing orthodontic treatment.