Various sites along the upper airway (UA) are prone to narrow and collapse in patients affected by obstructive sleep apnoea. Sleep stages may eventually alter these sites. The present study was designed to determine the site(s) of UA obstruction and the influence of sleep stage on the pattern of obstruction. Twenty eight obstructive sleep apnoea patients underwent UA pressure measurements during polysomnography. Solid-state pressure sensors were located at the nasopharynx, oropharynx, tongue base, hypopharynx and oesophagus and the lower limit of UA obstruction was determined relying on the observed pressure pattern. The site of UA obstruction varied among consecutive apnoeas in all but two patients. The lower limit of UA obstruction was predominantly located at the nasoand oropharynx. Rapid eye movement (REM) sleep was associated with a tendency for obstruction to extend towards lower levels of the UA and nasopharyngeal occlusion was significantly less observed during REM compared to oropharyngeal obstruction. Upper airway obstruction involves more than one specific site of the upper airway in the majority of sleep apnoea patients. Obstruction at lower levels of the upper airway is more likely to be observed during rapid eye movement sleep.