Background: Many patients with resected, pathologic (p)stage I non-small cell lung cancer (NSCLC) are not adequately staged preoperatively or intraoperatively. Reported 5-year survival is about 65%. Recently, nonsurgical techniques are being offered to these patients. Methods: A prospective database was retrospectively reviewed. All patients had an integrated positron-emission tomography/computed tomography (CT) and CT scan, an R0 pulmonary resection with lung palpation, and complete thoracic lymphadenectomy. Results: From August 2002 until July 2008, 2171 patients presented with presumed, resectable NSCLC. Of these, 721 were clinically (c)staged I, and 1450 were (c)staged II, III, or IV. Of the 721 (c)stage I, 405 (56%) had (p)stage I disease; 101 (14%) were clinically over-staged (benign nodules). Of those with NSCLC, 32% were clinically under-staged (stage II or higher on path). The 5-year Kaplan-Meier survival rates were 80% for (p)stage IA, 72% for (p)stage IB (p = 0.026), and 87% for the 721 with (c)stage I disease. The median-follow up was 3.8 years. Conclusions: When patients with NCSLC are accurately staged preoperatively and undergo complete thoracic lymphadenectomy, the 5-year survival is 80% for (p)stage IA tumors and 87% for (c)stage I disease. About 32% of patients are under-staged (most commonly from nonimaged N2 disease) despite the liberal application of all of the techniques that assess mediastinal lymph nodes preoperatively. Thus surgical intervention offers improved staging with resection of unsuspected nodal or parenchymal disease. If stereotactic radiation and radiofrequency ablation are considered for patients with clinically staged I NSCLC, these results should be considered. © 2009 The Society of Thoracic Surgeons.