Working hypothesis and aims: Recently, it has become apparent that the evaluation of nasally expired nitric oxide (NO) constitutes a simple and non-invasive diagnostic method, which discriminates between PCD patients, PCD carriers and healthy controls at high rate of specificity and sensitivity. Testing is simple and last approximately one minute. We have recently identified a unique isolated Druze population with high prevalence of PCD. The high frequency of disease places this closed community at a high risk of undiagnosed PCD.