Colorectal cancer (CRC) remains a major public health problem in the United States and worldwide. The majority of patients who have CRC eventually present with metastatic disease. The overall therapeutic goals for most patients with metastatic CRC (mCRC) are to control the disease, prolong life span, and maximize quality of life. Therefore, the ratio of efficacy to toxicity is one of the most important factors in choosing among treatment options and sequencing regimens. In addition, the choice of first-line systemic therapy will affect the options for second-line treatment. Several newer cytotoxic agents for the treatment of mCRC have been approved during the past 2 decades by the US Food and Drug Administration (FDA), including irinotecan, oxaliplatin, and capecitabine. The combination of a fluoropyrimidine (5-fluorouracil or capecitabine) with either oxaliplatin or irinotecan has been widely accepted as standard cytotoxic chemotherapy for either the first- or second-line treatment of mCRC. The FDA has approved several pathway-targeting agents for the treatment of mCRC; these include agents that target the vascular endothelial growth factor receptor pathway (bevacizumab, ziv-aflibercept, and ramucirumab) and those that target the epidermal growth factor receptor pathway (cetuximab and panitumumab). Here, we review the current clinical options for the second-line treatment of mCRC and the rationales for their use.