INTRODUCTION : Microcirculatory blood flow, and notably gut perfusion, is important in the development of multiple organ failure in septic shock. We compared the effects of dopexamine and norepinephrine (noradrenaline) with those of epinephrine (adrenaline) on gastric mucosal blood flow (GMBF) in patients with septic shock. The effects of these drugs on oxidative stress were also assessed. METHODS : This was a prospective randomized study performed in a surgical intensive care unit among adults fulfilling usual criteria for septic shock. Systemic and pulmonary hemodynamics, GMBF (laser-Doppler) and malondialdehyde were assessed just before catecholamine infusion (T0), as soon as mean arterial pressure (MAP) reached 70 to 80 mmHg (T1), and 2 hours (T2) and 6 hours (T3) after T1. Drugs were titrated from 0.2 mug kg-1 min-1 with 0.2 mug kg-1 min-1 increments every 3 minutes for epinephrine and norepinephrine, and from 0.5 mug kg-1 min-1 with 0.5 mug kg-1 min-1 increments every 3 minutes for dopexamine. RESULTS : Twenty-two patients were included (10 receiving epinephrine, 12 receiving dopexamine-norepinephrine). There was no significant difference between groups on MAP at T0, T1, T2, and T3. Heart rate and cardiac output increased significantly more with epinephrine than with dopexamine-norepinephrine, whereas. GMBF increased significantly more with dopexamine-norepinephrine than with epinephrine between T1 and T3 (median values 106, 137, 133, and 165 versus 76, 91, 90, and 125 units of relative flux at T0, T1, T2 and T3, respectively). Malondialdehyde similarly increased in both groups between T1 and T3. CONCLUSION : In septic shock, at doses that induced the same effect on MAP, dopexamine-norepinephrine enhanced GMBF more than epinephrine did. No difference was observed on oxidative stress.