The main pathological event of obstructive sleep apnea hypopnea syndrome (OSAHS) is the apneic collapse of the upper airways (UA). Frequently, UA collapse occurs at the same time at different section levels. dentifying the site and the dynamic pattern of obstruction is mandatory in therapeutical decision-making, and in particular if a surgical therapy option is taken into account. Nowadays, awake fiberoptic nasopharyngeal endoscopy represents the first level diagnostic technique to be performed in such patients, but recently, the drug-induced sleep endoscopy (DISE) has been introduced to overcome the limits of the awake nasopharyngeal endoscopy. Whatever diagnostic tool we decide to use, one of the main problems encountered is the standardization of the description of the sites and dynamic patterns of UA collapses. In this paper, the authors describe the NOHL classification, which could be applied during awake and sleep endoscopy, and allows a simple, quick, and effective evaluation of grade and patterns of UA collapse, suggesting its application, especially in therapeutical decision-making and in the analysis of surgical outcomes.© 2012 Springer-Verlag.