Animal studies implicate gut bacterial translocation via the portal vein as a major factor in the pathogenesis of postinjury multiple organ failure (MOF). We therefore inserted portal vein catheters for sequential blood sampling in the operating room, at 6, 12, 24, and 48 hours, and 5 days postoperatively in 20 injured patients (13 blunt, seven penetrating; mean age, 34 years) requiring emergent laparotomy and who were at known risk for MOF. The mean Revised Trauma Score was 6.4 ± 0.4, and the Injury Severity Score, 29.3 ± 2.3. Twelve (60%) patients arrived in shock (SBP < 90 torr). Eight (2%) of 212 portal blood cultures were positive; seven were presumed contaminants. The only positive systemic culture (total, 212) was a Staphylococcus aureus on day 5 in a patient with a concurrent staphyloccal pneumonia. In the first 48 hours, we could not detect endotoxin in portal or systemic blood. Additionally, simultaneous portal and systemic blood levels of complement fragment C3a, tumor necrosis factor, and interleukin-6 were nearly identical and, specifically, were not different in those patients who developed MOF. In summary, this prospective clinical study has not confirmed portal or systemic bacteremia within the first 5 days postinjury, despite an eventual 30% incidence of MOF.