Human lung cancers are divided into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), the two types having distinct clinical, histological, and biological features. Clinically, SCLC tends to present as a disseminated cancer that is not amenable to surgical resection and is treated with systemic chemotherapy and/or radiotherapy. SCLC cells typically contain dense neurosecretory granules measuring 80-90 nm in diameter. The granules contain hormones and neuropeptides that biologically characterize the neuroendocrine phenotype of SCLC. Specific neuropeptides and other neuroendocrine markers are discussed here, both in the context of their biological implications in SCLC, and for their potential as specific markers of disease and neuroendocrine progression.