According to American academy of sleep medicine, "Obstructive sleep apnea (OSA) is a sleep-related breathing disorder that involves a decrease or complete halt in airflow despite an ongoing effort to breathe." It occurs due to collapse of the pharyngeal airway due to lack of motor tonicity of the tongue or the dilator muscles or both. In this book special emphasis is given on different methods of its diagnosis and treatment modalities. OSA is also associated with various systemic diseases. Snoring and daytime sleepiness are some special features of this disease which are discussed in detail in this book. Different treatment options ranging from conservative to surgical modalities are further discussed.