RATIONALE AND OBJECTIVES To evaluate the effects of hepatic artery embolization (HAE), hepatic microcirculatory changes induced by HAE were assessed quantitatively in rats. METHODS Using in vivo microscopy, the blood-flow velocity (BFV) through terminal portal venules (TPVs) and terminal hepatic venules (THVs) was measured during HAE with gelatin sponge powder (GSP), iodized oil (Lipiodol, 0.1, 0.2, and 0.4 mL/kg), or 0.1 mL/kg Lipiodol followed by GSP. RESULTS After HAE with GSP, BFV through TPVs decreased significantly, but BFV through THVs did not decrease. After HAE with Lipiodol (0.2 and 0.4 mL/kg), BFV through TPVs decreased significantly, but BFV through THVs did not. After HAE with Lipiodol followed by GSP, BFV through both TPVs and THVs decreased significantly. CONCLUSIONS Neither GSP nor Lipiodol adversely affects hepatic microcirculation when administered alone; however, HAE with a combination of Lipiodol and GSP does adversely affect hepatic microcirculation.