1. Introduction.- 2. OSA, the magnitude of the problem  3 -- Compliance of various forms of OSA treatment -- 4.  Prevalence of positional obstructive sleep apnea in patients undergoing polysomnography and the effect of sleep stage -- 5  The contribution of head position to the apnea hypopnea index in patients with position dependent obstructive sleep apnea -- 6. Influence of sleep position on the transition of mild to moderate and severe OSA -- 7. Clinical characteristics of positional obstructive sleep apnea among Asians.- 8. Positional therapy: left lateral decubitus position versus right lateral decubitus position -- 9.  Drug Induced Sleep Endoscopy and Sleep Position.- 10.  Changes in site of obstruction in obstructive sleep apnea patients according to sleep position.- 11. Towards a clinical classification system (APOC) for positional dependent obstructive sleep apnea -- 12. Retrospective cohort analysis with the APOC system.-  13. Correlation between calculated/predicted and actual AHI after positional therapy.- 14.  Influence of sleep position on snoring -- 15. The effect of body position on sleep apnea in children.-  16.  Sleep position and pregnancy -- 17.  Positional OSA in Down syndrome.- 18. Positional OSA in the morbidly obese and the effect of weight loss on OSA severity.- 19.  The impact of body weight changes on body posture dominance in adult Obstructive Sleep Apnea Patients.- 20.  Positional central sleep apnea -- 21.  History of positional therapy: transition from tennis balls to new devices -- 22.  Long term results and compliance of a special vest preventing the supine position.- 23.  Results of a first generation new device for positional therapy -- 24.  Short term (4 weeks) results of the Sleep Position Trainer for positional therapy.- 25.  Long-term (6 months) effectiveness, compliance and subjective sleep outcomes of treatment with the Sleep Position Trainer in a large cohort of position-dependent OSApatients.- 26.  10 problems and solutions for Positional Therapy: Technical aspects of the Sleep Position Trainer -- 27.  Prevalence and Effect of supine-dependent obstructive sleep apnea and effect of oral appliance therapy.- 28.  Positional therapy and palatal surgery -- 29.  Positional therapy and tongue base surgery.- 30.  Residual POSA after maxillomandibular ad-vancement in patients with severe OSA.- 31.  Impact of upper airway surgery on positional change during sleep.- 32.  Comparison of positional therapy to CPAP in patients with positional obstructive sleep apnea .- 33.  Position training: an indispensable therapy.- 34.  Positional therapy, consequences for and implementation in OSA guidelines.-   35.- Position-dependent sleep apnea: implications for diagnosis and management.- 36.  Positional Therapy in Obstructive Sleep Apnea: For whom and for whom not.- 37.  Summary and future perspectives.