Regional perfusion and vascular resistance were examined in different tissues with the radioactive microsphere technique in Göttingen minipigs before, during and after treatment with Intralipid and heparin. This treatment led to an increase in the free fatty acid/albumin molar ratio from 0.39 +/- 0.23 to 3.43 +/- 1.37. Concomitantly a decrease in regional perfusion and an increase in regional vascular resistance was found in skin, adipose tissue, skeletal muscle, kidney, the gastro-intestinal tract, the thyroid and pancreas, while heart and liver showed vasodilatation. The vascular effects were fully reversible when the free fatty acid/albumin molar ratio had normalized. This vascular effect of lipid emulsions has to be considered when patients are treated with parenteral nutrition.