To compare the volumetric increase of segments 2 and 3, segment 4, and the caudate lobe after portal vein ligation (PVL) and portal vein embolization (PVE). The small size of the remnant liver and chemotherapy-induced liver injury increase the risk of postoperative hepatic insufficiency after major hepatic resection for colorectal liver metastases. Portal vein ligation has been suggested to be less effective than embolization in inducing hypertrophy of the remnant liver. We retrospectively reviewed 48 patients with colorectal liver metastases who underwent PVL (n = 17) or PVE (n = 31) at the Istituto per la Ricerca e la Cura del Cancro or the Institut Paoli-Calmette from March 1, 2000, through August 31, 2006. To compare the volume increase of segments 2 and 3, segment 4, and of the caudate lobe in patients who have undergone PVL or PVE in preparation for a major hepatic resection. There were no deaths related to PVE or PVL. Portal vein ligation was associated with resection of synchronous colorectal cancer in 16 patients. Resection of a liver metastasis in the remnant liver was performed in 11 patients. The median estimated baseline volume of segments 2 and 3 was 17.7% in the PVL group and 17.5% in the PVE group (P = .72). After PVL or PVE, it increased to 26.9% and 24.7%, respectively (P = .95), for volumetric increases of 43.1% and 53.4%, respectively (P = .39). The volumetric increases of segment 4 and the caudate lobe were similar. Portal vein ligation is as effective as PVE in inducing hypertrophy of the remnant liver volume.