After progression following first-line treatment, many patients with advanced non-small-cell lung cancer (NSCLC) still have a good performance status and can be considered for further treatments. Based on 2 randomized phase III trials, docetaxel was the first approved second-line therapy associated with longer survival and better quality of life compared with best supportive care alone and vinorelbine or ifosfamide. Since then, other agents have been approved for the second-line treatment of NSCLC (ie, pemetrexed, erlotinib, and gefitinib). Recently, new molecular-targeted agents are being increasingly considered in this setting, above all, bevacizumab and vandetanib. The discovery and validation of predictive markers of efficacy for both chemotherapy drugs and the new targeted therapies is of primary importance for the selection of second-line treatment for all patients with advanced NSCLC.