Chest radiography in patients with cystic fibrosis (CF) frequently shows more severe changes in the upper lobes. We performed bronchoalveolar lavage (BAL) on 12 clinically stable, young adult patients with CF to determine whether inflammation varies significantly among geographically distinct areas of the lung. We found that absolute numbers of neutrophils were generally greater in BAL fluid from the upper lobe (25.7 +/- 7.9 x 10(5) neutrophils/ml [mean +/- SEM]) of the right lung than that obtained from the right lower lobe (6.8 +/- 2.8 x 10(5) neutrophils/ml; p < 0.01). The mean value of unopposed neutrophil elastase activity in upper-lobe BAL fluid (227 +/- 91 nmol peptide hydrolyzed/ml/min) was also significantly greater than that in lower-lobe BAL fluid (84 +/- 43 nmol/peptide hydrolyzed/ml/ min; p < 0.01), and similar differences were found for myeloperoxidase activity and DNA content. Neutrophil influx and unopposed neutrophil elastase for a given region correlated inversely with lung function or percentage of ideal body weight, and upper-versus lower-lobe differences were more pronounced in subjects with better preservation of lung function. Our findings suggest that regional variation in inflammation must be considered when utilizing BAL to study lower respiratory tract inflammation in CF or to monitor responses to therapeutic interventions that can potentially diminish lung inflammation. Our findings may also have implications for the study of the natural history of lung inflammation and infection in neonates, infants, and young children with CF.