The aim of the study was to investigate interleukin 8 (IL-8) mRNA gene expression in circulating and emigrated intra-abdominal neutrophils during human secondary peritonitis intra- and postoperatively (until 96 h). Patients with secondary peritonitis were allocated to two groups, e.g., patients with no complications (n = 10) and patients with complications (organ failure, septic shock, etc., n = 9). Patients with elective abdominal surgery (n = 11) and a group with healthy volunteers (n = 7) were studied as controls. Neutrophil RNA was isolated and semiquantitative reverse transcription-PCR was performed. The PCR products were compared with corresponding GAPDH bands (=100%). The highest amount of IL-8 mRNA could be assessed in blood neutrophils of healthy volunteers (87.4% +/- 7.4%). Complicated peritonitis was associated with the lowest concentration of IL-8 mRNA in blood neutrophils intraoperatively (24% +/- 7%, P < 0.05), which showed no recovery throughout the observation period (34% +/- 8%, 96 h postoperatively). IL-8 mRNA concentration in blood neutrophils of patients with uncomplicated peritonitis and patients with elective abdominal surgery was higher intraoperatively (55.2% +/- 9% (uncomplicated peritonitis); 68% +/- 15% (elective abdominal surgery, P < 0.05 versus complicated peritonitis). Thereafter, IL-8 mRNA decreased slightly in both groups, but was distinctly higher than in patients with complicated peritonitis. Emigration to the abdominal cavity resulted in an approximately 2-fold, in some cases 3-fold, increase in the concentration of IL-8 mRNA in emigrated intra-abdominal neutrophils when compared with circulating cells. This increase could be observed in all groups. The long-lasting down-regulation of constitutive gene expression of IL-8 mRNA in blood neutrophils during complicated peritonitis is worrying because IL-8 is an important activator and chemoattractant for neutrophils themselves. It is encouraging that migration to another compartment, e.g., infected abdominal cavity, resulted in an increase in neutrophil IL-8 mRNA during complicated and uncomplicated peritonitis.