In a prospective study hemodynamic effects of dobutamine or dopamine (10 micrograms/kg/min) were investigated in 20 preterm infants who had protracted arterial hypotension refractory to volume therapy. Doppler ultrasonography of the superior mesenteric artery (SMA) was applied to verify intestinal perfusion and blood pressure was recorded in parallel. Mean arterial pressure (MAP) raised significantly in both groups (from 31.0 +/- 6.8 to 37.7 +/- 9.8 mm Hg during dobutamine and from 27.7 +/- 3.6 to 36.0 +/- 9.3 mm Hg during dopamine). Mean blood flow velocity increased from 25.8 +/- 13.5 to 31.5 +/- 16 cm/s with dobutamine and from 16.3 +/- 5.0 to 19.0 +/- 6.0 cm/s with dopamine (significant for dobutamine). Vascular resistance of SMA (indicated by resistance index; RI) decreased from 0.81 +/- 0.07 to 0.74 +/- 0.11 for dobutamine and from 0.89 +/- 0.06 to 0.79 +/- 0.07 for dopamine (significant for both groups). These data indicate that in the dose tested here both catecholamines are equally effective in raising MAP and lead to a significant increase of intestinal perfusion. Thus, a negative impact on mesenteric blood supply, predisposing to necrotizing enterocolitis, is not probable.