Lung cancer is the leading worldwide cause of cancer death and the majority of patients present with metastatic stage IV disease. At diagnosis, clinical, histologic, and molecular features must be considered in therapeutic decision-making for systemic therapy. Molecular testing for at least epidermal growth factor receptor (EGFR) and ALK should be performed in all patients before therapy. Platinum doublet chemotherapy may be considered for "fit" patients who do not have a molecular driver genetic abnormality. Bevacizumab can be considered for addition to the doublet in patients with nonsquamous cancers who have no contraindications. A pemetrexed combination is considered only in nonsquamous histology. Patients with EGFR mutations or ALK fusions should be treated with erlotinib or crizotinib, respectively, even in patients with tumor-related poor performance. The tyrosine-kinase inhibitors (TKIs) may be continued until multisite, symptomatic progression. For patients initially treated with a platinum doublet, maintenance chemotherapy with pemetrexed, erlotinib, gemcitabine, or possibly docetaxel is an option with selection based on clinical features, histology, type of initial therapy, and response to first-line therapy.