The cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-8 (IL-8), and intercellular adhesion molecule-1 (ICAM-1) have important roles in regulating neutrophil migration and the inflammatory response. To determine whether the concentration of these cytokines and soluble ICAM-1 (sICAM-1) in sputum was increased in patients with cystic fibrosis during acute exacerbations, we conducted (1) a cross-sectional study of 40 patients, 22 who were clinically well and 18 with acute pulmonary exacerbations; and (2) an 11 months longitudinal study of 16 patients. Significant differences in clinical scores, pulmonary function, and sputum neutrophil density were found between the acutely ill and the well group. There was a strong linear relationship (P < 0.0005) between TNF-alpha and IL-8 concentrations in sputum, but no association between clinical status and cytokine concentrations. The concentration of sICAM-1 was lower in acutely ill compared with well patients in the cross-sectional study. Recovery of exogenous IL-8 added to sputum was complete, while recovery of TNF-alpha averaged 70%. Recovery of exogenous sICAM-1 was only 43%, and the recoveries were lower in sputum samples from acutely ill patients than those from stable patients (P = 0.018). These data indicate that in cystic fibrosis patients, sputum concentrations of TNF-alpha and IL-8 are not increased during acute exacerbations of pulmonary inflammation.