Background: A unique substance reflecting the degree of inflammation localized to the lower respiratory tract in patients with cystic fibrosis (CF) has been the concern of several investigators and nitric oxide has gained interest for this purpose in the last decades. Objectives: The aim of this study was to evaluate the cytokine and nitrite levels by showing the relationship between them in serum and bronchoalveolar lavage fluid (BALF) of patients with CF and patients in which flexible fiberoptic bronchoscopy (FFB) was applied because of indications other than infection. Methods: 20 children with CF with mean age 8.2 years and 10 children as control group with mean age 4.2 years were included in the study. Cultures for aerobes, anaerobes, fungi and mycobacteria, cell differentials, cytokine and nitrite measurements were made from BALF specimens. White blood cell (WBC) count, erythrocyte sedimentation rate (ESR), quantitative C-reactive protein (QCRP), cytokine and nitrite levels were measured from serum samples. Results: BALF neutrophil, TNF-alpha, IL-8 and nitrite levels were significantly higher in patients with CF than control patients. There was no correlation between serum and BALF cytokine and nitrite levels. However, there was a significantly positive correlation between BALF IL-8 and nitrite levels in patients with CF ( r = 0.5) and also in control patients ( r = 0.6). Conclusions: The results suggest that BALF nitrite levels reflect the degree of inflammation localized to lower respiratory tract and may be a useful indicator of airway inflammation for patients with CF. Copyright (C) 2004 S. Karger AG, Basel.