OBJECTIVE To define the long-term outcome and treatment complications for patients undergoing liver resection for multiple, bilobar hepatic metastases from colorectal cancer. METHODS A retrospective analysis of 165 consecutive patients undergoing liver resection for metastatic colorectal cancer was performed. Patients were divided into a simple hepatic metastasis group, consisting of patients with three or fewer metastases in a unilobar distribution, and a complex hepatic metastases group, consisting of patients with four or more unilobar metastases or at least two bilobar metastases. RESULTS The 5-year survival rate was 36% for the simple group and 37% for the complex group. Multivariate analysis revealed that the number of hepatic segments involved by tumor and the maximum diameter of the largest metastasis correlated significantly with the 5-year survival rate. The surgical death rate was 4.9% for the simple group and 9.1% for the complex group; this difference was not significant. Multivariate analysis revealed that extended lobar resection and concomitant colon and hepatic resection were significant and independent predictors of surgical death. The combination of extended lobar resection and concomitant colon resection was used significantly more frequently in the complex group than in the simple group. CONCLUSIONS Resection of complex hepatic metastases, as defined in this study, results in a 5-year survival rate of 37% and confers the same survival benefit as does resection of limited hepatic metastases. The surgical death rate for this aggressive approach is significantly higher if extended lobar resections are necessary and if concomitant colorectal resection is performed. Patients who have complex hepatic metastases at the time of diagnosis of the primary colorectal cancer and who would require extended hepatic lobectomy should have hepatic resection delayed for at least 3 months after colon resection.