Airway inflammation plays an important role in diseases such as asthma, bronchiectasis, cystic fibrosis and chronic obstructive pulmonary disease. The use of non-invasive techniques for the evaluation of these inflammatory diseases has been the object of increasing interest in the past few years. The ollection of expired breath condensate (EBC) is achieved by freezing the exhaled air with the use of special condensing devices and provides useful information about areas of the respiratory tract accessible exclusively with invasive techniques. In the exhaled breath condensate there have been measured molecules, such as hydrogen peroxide, 8-isoprostane, end products of NO metabolism (nitrites/nitrates, nitrotyrosine), leukotrienes and, recently, pH. These measurements have given useful information regarding the inflammatory pathophysiology of airway diseases. Despite the methodological problems of this procedure, its non-invasive nature gives the opportunity for repeated measurements on the same person and provides valuable information for the assessment of airway inflammation. Pneumon 2004, 17(1):39-44.