BACKGROUND: The aim of this study was to compare postoperative outcomes of patients with synchronous colorectal liver metastases treated with either simultaneous or staged colectomy and hepatectomy. STUDY DESIGN: From July 1997 to June 2008, a review of our 1,344-patient prospective hepato-pancreatico-biliary database identified 230 patients treated Surgically for primary adenocarcinoma of the large bowel and synchronous hepatic metastasis. Clinicopathologic, operative, and perioperative data, complications, and grade of complications (grade 1, minor, to grade 5, death) were reviewed to evaluate selection criteria, operative methods, and perioperative outcomes. Chi-square and proportional hazard model were used to evaluate predictors of outcomes. RESULTS: Severity patients underwent simultaneous resection of colon primary and liver metastasis in a single operation; 160 patients underwent staged operations. Simultaneous resections were similar for size (median 4 cm versus 3.7 cm) and number (median 3 cm versus 3 cm) of liver metastases. Major liver resections (>= 3 Couinaud segments) were similar between staged and simultaneous (32% versus 33%, respectively), as was type of colectomy (p = 0.2). Complication rates and severity were similar in both groups: 39 of 70 patients (56%) in the Simultaneous group experienced 63 complications versus 88 of 160 patients (55%) with 162 complications in the staged group (p = 0.24). Multivariate analysis identified blood transfusion as a predictor of complication (odds ratio 2.98, p = 0.001). Patients having simultaneous resection required fewer days in the hospital (median 10 days versus 18 days, p = 0.001). CONCLUSIONS: By avoiding a second laparotomy, simultaneous colon and hepatic resection reduces overall hospital stay, with no difference in morbidity and mortality rates or in severity of complications, compared with staged resection. Simultaneous resection is an acceptable option in patients with resectable synchronous colorectal metastasis. (J Am Coll Surg 2009;208:842-852. (C) 2009 by the American College of Surgeons)