The influence of a moderate, standardized trauma on bacterial and endotoxin kinetics in post-traumatic Escherichia coli septicemia was studied in a porcine model. Septicemia was induced by intravenous infusion of live E. coli (2.5 x 10(9) cfu/kg, rough:K5:H6) into 14 piglets. Seven of these animals had been exposed to moderate trauma 48 hours previously. Following the E. coli infusion, cardiovascular signs of severe septicemia appeared in all the piglets, associated with gradual increase in the blood bacterial count and the plasma levels of endotoxin. This increase was significantly less pronounced in the animals with prior moderate trauma than in the nontraumatized animals. Thus no depression of the host defense system was demonstrable 2 days after moderate trauma.