One of the most important parts of the management of patients with the obstructive sleep apnoea syndrome is the assessment of the level of obstruction in order to allow the appropriate choice of treatment. We have recently developed the technique of sleep nasendoscopy which allows direct visualization of the site of obstruction in the sleeping patient. Having performed over a hundred of these investigations we are able to suggest a grading system for these patients dividing them into five grades. Grade 1 = simple palatal level snoring; grade 2 = single palatal level obstruction; grade 3 = palatal level obstruction with intermittent orohypopharyngeal involvement; grade 4 = sustained multi-segment involvement; grade 5 = tongue-base level obstruction. We feel that this grading system will help in deciding which patients are suitable for surgery and which are not; hence avoiding unnecessary operations and allowing a more logical decision on the appropriate form of treatment. Results of the first 90 patients to have sleep nasendoscopy are presented.