This study was designed to examine the response of the baboon during a 24 hr period following live Escherichia coli organism infusion. Experiments were performed on 10 young adult adolescent baboons. Eight of the baboons received a mean concentration of 1.5 × 1010 organisms/kg infused during a 30 to 360 min period. Two control baboons received anesthesia and 0.9% sodium chloride solution during the 24 hr period. Heart, lung, liver, and kidney were evaluated with both light and electron microscopy and the morphologic data were interrelated with the physiologic data. The acute lung lesion seen in 2 to 6 hr studies was not found in this prolonged shock model. Both the liver and kidney exhibited dysfunction; these pathophysiologic alterations were accompanied by morphologic changes. Sinusoidal fibrin thrombi and hepatocyte damage were observed in the liver, and were associated with increases in LDH, FLDH, and hypoglycemia. Glomerular fibrin thrombi and tubular epithelial changes of cytoplasmic vacuolization and brush border loss were present in the kidney, and an increase in BUN levels was noted. Our data would indicate that the live E. coli infusion baboon model shows pathologic and physiologic derangements quite similar to those reported in the patient in septic shock.