Background: Meningococcal infection is still a serious disease in the 21st century infecting 0.5 ¡V 1.2 millions yearly, mainly children, killing 1 in 10 in spite of optimal treatment. Lipopolysaccharide (LPS), a glycolipid in the outer membrane of Neisseria meningitidis, is the principle toxic component of the bacterium. Objective: To study: 1) the association between laboratory parameters in serum and cerebrospinal fluid (CSF) and the severity of the infection (shock versus non-shock) and 2) the association between the levels of LPS in plasma and CSF and 23 different laboratory parameters. Methods: We studied retrospectively 23 different laboratory parameters determined at hospital admission for 76 patients admitted from 1983 to 1989. All patients had confirmed infection with Neisseria meningitidis. The patients were dichotomised into one group developing persistent shock (n = 22, shock) and one normotensive group (n=55, non-shock). The data were analysed with non-parametric statistical methods.Results: We found a statistical significant difference between shock and non-shock patients for 20 of the 23 parameters examined. Fifteen of the 20 parameters in serum and all three parameters in the CSF showed a statistically significant correlation to LPS. Erythrocyte sedimentation rate (ESR) <20 mm/h, leukocytes <3.5x109/l, pH <7.30, CRP <150mg/l and creatinine >125 Ýmol/l on admission were associated with the development of persistent septic shock.Conclusion: The massive inflammatory response in the circulation induced primarily by LPS in N. meningitidis alters various parameters routinely measured in plasma. However, the changes are unspecific, and for most parameters except ESR, leukocytes, pH, CRP and creatinine, they can not be used to predict the development of persistent shock.