['The aim of this study was to investigate whether physical evaluations could be used for predicting the presence and severity of obstructive sleep apnea (OSA) in non-obese snoring patients.', 'This is a retrospective study, and a total of 244 non-obese (body mass index, BMI, <27 kg/m(2)) snoring patients (178 men and 66 women; mean age = 43.1 ± 12.1 years) were included. Each patient underwent polysomnography and a thorough physical examination, including flexible nasopharyngoscopy and Müller maneuver. Patients were divided into four groups based on apnea-hypopnea index (AHI) scores: normal (simple snoring), AHI < 5; mild OSA, 5 ≦ AHI < 15; moderate OSA, 15 ≦ AHI < 30; severe OSA, AHI ≧ 30. Logistic regression was used to identify risk factors for OSA severity.', 'Fifty-nine patients (24%) were simple snorers. The prevalence of sleep apnea (mild, moderate, or severe OSA) for our non-obese snoring patients was 76%. Univariate logistic analyses showed that higher BMI, male gender and retropalatal Müller grades were significantly associated with OSA severity. Multivariate logistic regression analysis identified male gender and retropalatal Müller grade as risk factors for OSA in non-obese snoring patients.'] Is retropalatal Müller grade associated with the severity of obstructive sleep apnea in non-obese Asian patients . Retropalatal Müller grade and OSA in non-obese?