The aim of this study was to examine an acoustic reflection method using a flexible tube for identifying the obstructive site of the upper airway in snorers and patients with obstructive sleep apnoea (OSA). As a preliminary study it was performed n models and subjects in the awake state. Flextube narrowing was produced in a model of the nose and pharynx and three blinded observers assessed the obstructive level. The correlation between pharyngeal narrowing assessed by endoscopy and by acoustic measurement during Müller manoeuvres was also examined in 10 OSA patients and 11 healthy non-snoring, adults. Three blinded observers dentified the level of 176 of 180 random cases of flextube narrowing in a polycarbonate model correctly The level of narrowing was always correctly evaluated within 1.9 mm. Pharyngeal area decrease was measured by the flextube method during the Müller manoeuvre but it was not closely related to the findings by endoscopy. In conclusion the flextube reflectometry method was able to demonstrate narrowng in a model of the nose and pharynx in a precise way. Narrowing was also observed during Müller manoeuvres. Flextube reflectometry may be a promising method to detect upper airway narrowing but further evaluation during sleep is required.