Hepatic wedge resection for colorectal liver metastasis has been reported to have a high incidence of positive surgical margins. Anatomic segmental resection is now widely practiced, although there are few data comparing segmental and wedge resection in terms of tumor clearance or long-term outcome. There were 267 patients who underwent liver resection for metastatic colorectal cancer between July 1985 and October 1998 at our institution who had either a wedge (n = 119) or segmental (n = 148) resection. Patient, tumor, and treatment data were compared, actuarial survival was determined, and prognostic factors were analyzed. Anatomic segmental resection was associated with similar blood loss, operative time, and complications as wedge resection. Segmental resection had a significantly lower rate of positive margins (2% vs. 16%) compared to wedge hepatectomy (P <0.001). On univariate analysis, segmentectomy resulted in longer survival with a median of 53 months vs. 38 months for wedge hepatectomy (P = 0.015). Preoperative carcinoembryonic antigen level, positive margin of resection, and the presence of extrahepatic disease independently predicted survival on multivariate analysis. Anatomic segmental resection is a safe procedure and is superior to wedge resection as an oncologic operation for colorectal liver metastasis because it results in better tumor clearance and improved survival.