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 OSA patients.- 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.