This was a prospective study of a new objective method which quantitatively analyses the upper airways in patients with obstructive sleep apnoea (OSA). Video-nasopharyngoscopic examinations of the upper airways of 45 patients were carried out with an endoscopic calibrator. Images of the upper airway during quiet respiration and Mueller's manoeuvre in erect and supine positions were digitized by computer to generate the actual dimensions of obstructive sites. Measurements by the new method were validated by comparing 90 pairs of videoendoscopic images with upper airway magnetic resonance imaging (MRI) measurements at two identical levels. Quantitative precision is 100% for the retropalatal level and 95.6% for the retrolingual level with a tolerance of 0.5 cm(2) between the two methods. The absolute mean of the difference between the two methods of measurement is 0.08 cm(2) at the retropalatal level and 0.18 cm(2) at the retrolingual level. The agreement between the digital-imaging videoendoscopic and MRI measurements was 93.3% for the retropalatal level and 95.6% for the retrolingual level. Quantitative computer-assisted digital imaging is a reliable, cost-effective clinical method of upper airway evaluation in OSA patients. This method allows us to examine the dynamic and static morphology objectively, measure surgical outcomes of upper airway, opening up new avenues for OSA management.