Small cell lung cancer (SCLC) is an aggressive neuroendocrine tumor characterized by early metastatic spread and responsiveness to initial therapy. The incidence of SCLC has been declining in the United States in parallel with the decreasing prevalence of cigarette smoking. Limited stage disease is potentially curable with chemoradiotherapy followed by cranial irradiation. Extensive stage disease is incurable, but systemic chemotherapy can improve quality of life and prolong survival. Nearly all patients relapse with chemoresistant disease. Molecularly targeted therapy has failed to yield convincing clinical benefits. Nevertheless, many biologically rational strategies, including immune checkpoint inhibition, show promise in ongoing clinical trials.