Cytokines and polymorphonuclear leukocytes play a key role in immune mediated inflammation in progressive pulmonary damage due to cystic fibrosis. The aim of this study is to establish a simple measure of the host's propensity to secrete inflammatory cytokines and to correlate this with clinical status. Patients (n=44, median age 16 years) with the DeltaF 508 mutation (homozygous) were grouped according to their Shwachman score: Patients with mild disease (Shwachman score 71-100 points, group A, n=22, median FEV(1) 79%) were compared with those with more severe disease (Shwachman score 41-55 points, group B, n=22, median FEV(1) 55%) and age-matched controls (group C, n=22, median FEV(1) 102%). Whole blood was stimulated with 5 ng of lipopolysaccharide (LPS). Interleukin-8 (IL-8) was measured by chemiluminescent immunometric assay (DPC, Bad Nauheim, Germany). Though there was a significant difference at baseline for IL-8 (median group A/B/C 6.1/30.5/5.8 pg/ml; p<0.001), there was no significant difference after stimulation. Moreover, in Pseudomonas aeruginosa positive (Psa+) patients (n=26) there was a significant negative correlation (r=-0.539; p<0.004) between baseline IL-8 and FEV(1) (%). Clinical course and lung function (in Psa+) correlate with IL-8 levels.