Bronchiectasis is characterized by chronic inflammation in one or more bronchi, but the extent of inflammation is difficult to monitor. The concentration of nitric oxide (NO) in exhaled air is increased in asthmatic patients, possibly as a result of the chronic inflammatory process. We have measured exhaled NO in patients with documented bronchiectasis and investigated whether the concentration of exhaled NO is related to the extent of disease as defined by computed tomography (CT) and lung function. In 20 patients with bronchiectasis who were not taking inhaled steroids, the peak concentration of NO in exhaled air, measured by a modified chemiluminescence analyzer, was significantly elevated (285 +/- 49.0 ppb) as compared with values for 79 normal subjects (89 +/- 2.7 ppb, p < 0.01) and 19 patients with bronchiectasis treated with inhaled steroids (88 +/- 13.4 ppb, p < 0.01). Thin-section CT was used to quantify the extent of bronchiectasis in the 19 patients. There was a significant correlation between the CT score and FEV1 (r = 0.73, p < 0.01). In patients not treated with inhaled steroids there was a significant relationship between CT score and peak exhaled NO (r = 0.81, n = 12, p < 0.02), but this was not the case for patients treated with regular inhaled steroids (n = 7). We conclude that untreated bronchiectasis is associated with an increase in exhaled NO, and that this is correlated with disease severity, whereas patients treated with inhaled steroids have levels of exhaled NO within the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)