Purpose Provide evidence-based recommendations updating the 2015 ASCO guideline on systemic therapy for patients with stage IV non-small-cell lung cancer (NSCLC). Methods The ASCO NSCLC Expert Panel made recommendations based on a systematic review of randomized controlled trials from February 2014 to December 2016 plus the Cancer Care Ontario Program in Evidence-Based Care's update of a previous ASCO search. Results This guideline update reflects changes in evidence since the previous guideline update. Fourteen randomized controlled trials provide the evidence base; earlier phase trials also informed recommendation development. Recommendations New or revised recommendations include the following. Regarding first-line treatment for patients with non-squamous cell carcinoma or squamous cell carcinoma (without positive markers, eg, EGFR/ALK /ROS1), if the patient has high programmed death ligand 1 (PD-L1) expression, pembrolizumab should be used alone; if the patient has low PD-L1 expression, clinicians should offer standard chemotherapy. All other clinical scenarios follow 2015 recommendations. Regarding second-line treatment in patients who received first-line chemotherapy, without prior immune checkpoint therapy, if NSCLC tumor is positive for PD-L1 expression, clinicians should use single-agent nivolumab, pembrolizumab, or atezolizumab; if tumor has negative or unknown PD-L1 expression, clinicians should use nivolumab or atezolizumab. All immune checkpoint therapy is recommended alone plus in the absence of contraindications. For patients who received a prior first-line immune checkpoint inhibitor, clinicians should offer standard chemotherapy. For patients who cannot receive immune checkpoint inhibitor after chemotherapy, docetaxel is recommended; in patients with nonsquamous NSCLC, pemetrexed is recommended. In patients with a sensitizing EGFR mutation, disease progression after first-line epidermal growth factor receptor tyrosine kinase inhibitor therapy, and T790M mutation, osimertinib is recommended; if NSCLC lacks the T790M mutation, then chemotherapy is recommended. Patients with ROS1 gene rearrangement without prior crizotinib may be offered crizotinib, or if they previously received crizotinib, they may be offered chemotherapy.