Systemic vasodilatation in surfactant-depleted newborn piglets is induced by 200 mg/kg of modified porcine lung surfactant (Curosurf). The aim of this investigation was to study whether this effect is dependent on dose and could further be induced by instillation of a bovine surfactant preparation (Survanta). Twenty-two 3-5-d old piglets were subjected to repeated saline lung lavage and then randomized to one of three groups. Instillation of either Curosurf l00 mg/kg (n=8), Survanta l00 mg/kg (n=7) or Curosurf 200 mg/kg (n=7) was performed through the endotracheal tube. Systemic vascular resistance decreased 7 (+/-4)%, 15 (+/-12)% and 18 (+/-6)% in the three groups, respectively (p < 0.05 in all three groups). A significant difference between the high and low dose Curosurf groups was found (p < 0.05), whereas no significant difference was seen between the Curosurf 100 mg group and the Survanta group. The decrease in vascular resistance was compensated by an increase in cardiac output, resulting in a stable mean arterial blood pressure. In conclusion, both Curosurf and Survanta induce a significant decrease in systemic vascular resistance in surfactant-depleted newborn piglets. A more pronounced effect was observed after 200 mg/kg than after 100mg/kg of Curosurf.