Background and objective: In cystic fibrosis (CF) very few studies have assessed sputum 8-iso-PGF(2 alpha) levels during pulmonary exacerbations as a direct measure of airway oxidative stress. The role of other lipid-derived inflammatory mediators, such as the cysteinyl leukotrienes (cys-LTs) and prostaglandin (PG)-E-2, during exacerbations is also poorly defined and the effect of conventional antibiotic therapy on these components of the inflammatory process is unclear.Methods: Sputum 8-iso-PGF(2 alpha), total cys-LT and PGE(2) levels were measured in 17 CF patients experiencing a pulmonary exacerbation and repeated analysis were performed in 15 of these patients after antibiotic treatment. Eight stable CF and nine healthy subjects provided control data.Results: Sputum 8-iso-PGF(2 alpha) was significantly elevated in acute, but not stable CF patients versus healthy controls (P < 0.001). Similarly, sputum cys-LT and PGE(2) levels were increased in acute compared with stable CF patients and healthy controls (P <= 0.001). Although substantially lower than in acute patients, sputum cys-LT levels in stable patients were also significantly higher than in normal controls (P = 0.01). There were strong associations between cys-LT levels and sputum total cell counts, and blood neutrophils in acute patients (r(2) = 0.53, P = 0.001 and r(2) = 0.33, P < 0.05, respectively). Overall in the CF patients, FEV1%predicted was strongly and negatively correlated with sputum 8-iso-PGF(2 alpha) (r(2) = 0.34, P = 0.006), cys-LT (r(2) = 0.40, P = 0.002) and PGE(2) (r(2) = 0.52, P < 0.001) levels. Antibiotic treatment reduced sputum total cell count (P = 0.03), but did not affect 8-iso-PGF(2 alpha), cys-LT or PGE(2) levels.Conclusions: CF exacerbations are characterized by increased oxidative stress and sputum concentrations of bioactive lipid mediators. Treatment does not modulate these aspects of inflammation and more targeted therapy needs further study.