Objective: To examine the authors' experience with preoperative ipsilateral portal vein embolization (PVE) and assess its role in extended hepatectomy. Summary Background Data: Extended hepatectomy (five or more liver segments) has been associated with higher complication rates and increased postoperative liver dysfunction than have standard hepatic resections involving lesser volumes, Recently, PVE has been used in patients who have a predicted (postresection) future liver remnant (FLR) volume less than 25% of total liver volume in an attempt to increase the FLR and reduce complications. Methods: Sixty patients from 1996 to 2002 were reviewed. Thirty-nine patients had PVE preoperatively. Eight patients who had PVE were not resected either due to the discovery of additional unresectable disease after embolization but before surgery (n = 5) or due to unresectable disease at surgery (n = 3). Therefore, 31 patients who had PVE subsequently underwent extended hepatic lobectomy. A comparable cohort of 21 patients who had an extended hepatectomy without PVE were selected on the basis of demographic, tumor, and liver volume characteristics. Patients had colorectal liver metastases (n = 30), hepatocellular carcinoma (n = 15), Klatskin tumors (n = 9), peripheral cholangiocarcinoma (n = 3), and other tumors (n = 3). The 52 resections performed included 42 extended right hepatectomies, 6 extended left hepatectomies, and 4 right hepatectomies extended to include the middle hepatic vein and the caudate lobe but preserving the majority of segment 4. Concomitant vascular reconstruction of either the inferior vena cava or hepatic veins was performed in five patients. Results: There were no differences between PVE and non-PVE groups in terms of tumor number, tumor size, tumor type, surgical margin status, complexity of operation, or perioperative red cell transfusion requirements. The predicted FLR was similar between PVE and non-PVE groups at presentation. After PVE the FLR was higher than in the non-PVE group. No complications were observed after PVE before resection. There was no difference in postoperative mortality, with one death from liver failure in the non-PVE group and no operative mortality in the PVE group. Postoperative peak bilirubin was higher in the non-PVE than the PVE group, as were postoperative fresh-frozen plasma requirements. Liver failure (defined as the development of encephalopathy, ascites requiring sustained diuretics or paracentesis, or coagulopathy unresponsive to vitamin K requiring fresh-frozen plasma after the first 24 hours postresection) was higher in the non-PVE patients than the PVE patients. The hospital stay was longer in the non-PVE than the PVE group. Conclusions: Preoperative PVE is a safe and effective method of increasing the remnant liver volume before extended hepatectomy. Increasing the remnant liver volume in patients with estimated postresection volumes of less than 25% appears to reduce postoperative liver dysfunction.