The intensity of the host inflammatory response to pulmonary infection with Pseudomonas aeruginosa immediately prior to death was determined in six patients with cystic fibrosis (CF). Plasma concentrations of neutrophil elastase alpha 1-antiproteinase, tumour necrosis factor-alpha (TNF alpha) and serum C-reactive protein (CRP) were increased in the 7 days prior to death (P < 0.05) when compared with a period of clinical stability during the preceding 6 months. An increased inflammatory response was sustained for many weeks prior to death and was associated with poor symptom and lung function responses to apparently appropriate antibiotic treatment.