Abstract: This invention provides a purified endotoxin-induced thrombosis factor, preferably an endotoxin-induced thrombosis factor characterized by an apparent molecular weight between about 50,000 and 65,000 daltons, more specifically about 55,000 daltons, on reduced and nonreduced SDS-polyacrylamide gels, by maximal recovery on elution from such gels at 52,000 to 58,000 daltons, by the ability to migrate as a single band on such gels, by the ability to precipitate in ammonium sulfate at saturations from 40% to 70%, by the ability to precipitate in polyethylene glycol at concentrations above 15%, by high hydrophobicity, by the ability to bind weakly to a hydroxylapatite column and to a lentil lectin column, by the ability to bind tightly to a hydrophobic interaction resin and smear off with ethylene glycol, and by the ability to bind tightly to a reverse-phase column and elute more effectively with isopropranol than with acetonitrile, by the ability to bind to an anion exchange resin over a pH range from 5 to 10, by