We devised a method for portal vein embolization with ethanol injection (PVEEI) via a fine needle. Both the efficacy and safety of this procedure were evaluated in 28 dogs. An embolization of the left central and lateral lobes was undertaken with various doses of absolute (95%) ethanol. The smallest dose, 0.25 ml/kg ethanol (n = 7), caused the least damage to the liver, but the embolization was not complete. At the highest dose at 1.0 ml/kg, four of the seven dogs died of respiratory arrest; however, embolization was complete in the remaining dogs. All animals tolerated the procedure by 0.5 ml/kg ethanol (n = 11) with a satisfactory embolic effect, slight toxicity to the hepatic parenchyma, and only transient changes in liver function. The results suggested that PVEEI is safe and effective when a suitable dose of ethanol is administered. Local overembolization occurred in one dog due to extension of the thrombus, suggesting that the point of puncture should not be near the confluence of the branches. Since a selective portal venous puncture is not difficult to perform under sonographic guidance, PVEEI is expected to be clinically applied.