Accurate clinical staging is critical in the evaluation of any patient with non-small cell lung cancer (NSCLC). Staging for NSCLC is based on the tumor, node, metastasis (TNM) system used for most solid tumors. The clinical stage, as determined by all available clinical, radiographic, and biopsy data, provides patients and physicians with an overall assessment of disease extent and prediction of survival and enables the identification of appropriate therapies. It is thus imperative that staging be performed as accurately and comprehensively as possible while also maintaining efficiency. To do so requires an understanding of the staging system, the clinical clues that drive the staging evaluation, and a working knowledge of available noninvasive and invasive diagnostic modalities.