The most frequent cause of toxic shock in our area is meningococcal sepsis. It is currently assumed that endotoxin produce by this bacteria, a lipopolysaccharide with toxic properties, is able to trigger shock and DIC by stimulating both arachidonic acid pathways, among other actions. Previous studies in our laboratory demonstrated significant differences (p +/- 0.001) in the amounts of endotoxins released in vitro by strains from patients and healthy carriers and statistically related criteria of severity with mortality in 256 patients in our center over the last 10 years. In the present study we attempted to establish whether plasma levels of endotoxin were correlated with the severity of the disease. We studied 32 patients with meningococcal sepsis, dividing the subjects into two groups: those in whom six or more criteria of severity were present, and those in whom less than six criteria were found. Blood levels of endotoxin were determined upon admission and after the administration of antibiotics (penicillin and chloramphenicol) using the limulus test with a chromogenic substrate (Coatest, Endotoxin, Kabivitrum, Sweden). Levels of endotoxins were significantly higher in patients with more than six criteria of severity both upon admission (0.6 +/- 0.03) ng/ml) and 4 h. afterward (0.74 +/- 0.006 ng/ml) in comparison to children in whom the clinical picture was less serious (0.27 +/- 0.18 ng/ml and 0.27 +/- 0.18 ng/ml and 0.27 +/- 0.16 ng/ml7 t = 5.8 y t = 5.6 respectively. Endotoxin levels were highest in patients presenting shock, disseminated intravascular coagulation in the hypocoagulability phase and more than 8 criteria.(ABSTRACT TRUNCATED AT 250 WORDS)