Background. Although the initial response to sepsis includes a hyperdynamic phase and although the increased hepatic perfusion in early sepsis is due solely to the increased portal blood flow, it remains unknown whether the gut plays an important role in producing such a response. Materials and methods. Adult male Sprague-Dawley rats underwent a complete enterectomy (ER) before being subjected to sepsis by cecal ligation and puncture (CLP; the cecum was excised from the removed gut and stitched to the posterior peritoneum in ER groups) or sham operation. At 2 h after CLP (i.e., the early, hyperdynamic phase of sepsis), cardiac output and heart performance (±dP/dt(max)), as well as hepatic and renal blood flow, were measured. Systemic and regional oxygen delivery (DO2) and oxygen consumption (VO2) were also determined. Results. Cardiac output, heart performance, organ blood flow, as well as DO2 and VO2, increased significantly 2 h after CLP. ER prior to the onset of sepsis, however, prevented the elevation of those parameters. ER in sham animals did not alter the measured parameters with the exception that portal blood flow decreased by 85% and hepatic arterial blood flow increased by 368%, resulting in no significant reduction in hepatic DO2 and VO2. There were no changes in circulating blood volume among groups, indicating that the effect of ER on hemodynamics after CLP was not due to alterations in blood volume. Conclusion. Since ER immediately before the onset of sepsis prevents the increase in cardiac output and regional hemodynamics, the gut appears to play an important role in producing the hyperdynamic response during the early stage of polymicrobial sep- sis. (C) 2000 Academic Press.