OBJECTIVES:  Metastasectomy in patients with metastatic colorectal cancer (mCRC) is the best option to achieve long-term survival and offers the only chance for cure. Increasing the number of resectable patients is therefore a medical treatment goal. This study examines the trend over time in metastasectomy and pre-surgery chemo- and biologic therapy in newly diagnosed mCRC patients. METHODS:    Using a large, U.S. medical claims database from a national commercially-insured population, we identified patients with newly diagnosed mCRC between 2001 and 2005. Metastasectomy rates by anatomic location were assessed for all mCRC patients during one year after mCRC diagnosis. Chemotherapy and/or biological therapy within 90 days prior to the date of metastasectomy was evaluated. RESULTS:  A total of 1785 newly diagnosed mCRC patients were identified; of which 327 patients (18.3%) received metastasectomy within one year after mCRC diagnosis. This included 70 patients (3.9%) who were not initially resected but had metastasectomy following chemo- and/or biologic therapy. From 2001 to 2005, the most common surgery site was the liver (ranged 13.9% - 16.7%), followed by the lung (2.3% to 4.9%) and pelvic resection (0.0% - 0.5%).  The percentage of patients who were not initially resected and had metastasectomy after receiving chemo- and/or biologic therapy increased from 2.9% in 2001 to 5.6% in 2005. Among patients who received pre-surgery chemo- and/or biologic therapy, the percentage of receiving biologic therapy increased rapidly in 2004-2005 from 35.0% to 77.3%.   CONCLUSIONS:    The proportion of patients with mCRC undergoing metastasectomy increased over time and the percentage of patients who were not initially resected and had metastasectomy after receiving chemo- and/or biologic therapy almost doubled during the study period.