Sato S, et al. - This study was designed to shed light on the clinical role of fractional exhaled nitric oxide (FeNO) in asthmatic treatment. Findings demonstrated that during conventional treatment of asthma, a significantly strong correlation was obvious between FeNO level at diagnosis and the largest changes of FeNO values from diagnosis. As for the unlikely conventional parameters, no significant associations were observed between FeNO levels and deterioration of asthma during the treatment periods. In asthmatics, decreased lung function may be indicated by an elevated mean FeNO level.