Forty critically ill patients fulfilling the definitions of systemic inflammatory response syndrome were enrolled in a double-blind cross-over interventional study assessing the effects of dopexamine and prostacyclin on splanchnic perfusion, cardiovascular function and oxygen flux. The cross-over design involved either dopexamine (1.25 micrograms.kg-1.min-1) or prostacyclin (0.5 ng.kg-1.min-1) being infused for 6 h followed by a 12-h washout period prior to an identical infusion sequence using the other agent. Preliminary analysis revealed a significant period effect, so data from the second infusion period were excluded from further analysis. Dopexamine caused a significant increase in heart rate (116 vs. 106 beat.min-1), and urine output (103 vs. 69 ml.h-1). Dopexamine produced a significant increase in oxygen delivery (infusion 548 ml O2.min-1.m-2; no infusion 492 ml O2.min-1.m-2) while prostacyclin caused a decrease (infusion 460 ml O2.min-1.m-2; no infusion 547 ml O2.min-1.m-2). The results indicate that dopexamine improves oxygen delivery and urine output more effectively than prostacyclin.