The recent development of chemotherapeutic agents and biomarkers have remarkably improved treatment outcomes of metastatic colorectal cancer (mCRC). However, decision making regarding the choice of therapy for mCRC has been complicated by the availability of many different treatment options. In this review, we will discuss the clinical evidence for current systemic treatment, including the key roles of 3 cytotoxic drugs and oral fluoropyrimidines, the appropriate use of anti-VEGF and anti-EGFR therapy, the significance of RAS mutation status as a predictive marker for anti-EGFR therapy, and new agents for salvage therapy (regorafenib and TAS-102 [TFTD]).