This paper is divided into a retrospective descriptive section in which we report on three distinctly different and spontaneous responses of the baboon to LD100 Eschericia coli observed over the last 6 years. This section is followed by an experimental section in which we reproduce the immediate and delayed responses based on hypothetical mechanisms. In the descriptive section, we arbitrarily divided all the non-survivor animals on which we had sufficient data into three groups based on duration of survival (i.e., 12 hr or less, immediate, 12 to 30 hr, intermediate, and 30 hr or more, delayed). The natural history and pathophysiology of the 12 hr or less group matched that of capillary leak syndrome with a rapid fall in blood pressure, rise in hematocrit, massive edema, and congestion with leukocyte sequestration in both lung and liver, with only limited adrenal cortical hemorrhage. The 12 to 30 hr group matched the natural history of a consumptive hemorrhagic diatheses with a biophasic blood pressure response, limited change in hematocrit, a severe consumptive coagulopathy, severe adrenal cortical hemorrhage, and a moderate renal cortical tubular necrosis, but limited renal cortical thrombosis. The greater than 30 hr group matched the natural history of a microvascular thrombotic (hemolytic uremic) syndrome with a stable blood pressure, a fall in hematocrit associated with a massive renal cortical thrombosis with a severe medullary, and cortical tubular necrosis. We did not analyze these groups further (i.e., type of intervention etc.) once we found that time of survival correlated with a unique clinical syndrome, because based on these observations, we hypothesized that we could reproduce the immediate capillary leak and pulmonary failure, and the delayed microvascular thrombosis and renal failure syndromes experimentally. We reproduced the immediate (< 12 hr) and delayed (> 30 hr) responses by infusion of either tumor necrosis factor or C4b binding protein with sublethal E. coli. This provides models of the immediate and delayed as well as the intermediate responses to E. coli for study of mechanism and the efficacy of therapeutic interventions.