['Essentials The procoagulant effects of microparticles (MPs) on coagulation in endotoxemia are not known. MPs from endotoxemia volunteers were evaluated for procoagulant activity in a plasma milieu. MPs from endotoxemia volunteers shortened clotting times and enhanced thrombin generation. MP procoagulant effects were mediated in a factor XI-dependent manner.'] Do procoagulant microparticles promote coagulation in a factor XI-dependent manner in human endotoxemia?