<jats:sec><jats:title>Purpose</jats:title><jats:p> Epidermal growth factor receptor (EGFR) –tyrosine kinase inhibitors have proven efficacy in advanced non–small-cell lung cancer (NSCLC). We hypothesized that erlotinib would be efficacious in the adjuvant setting. </jats:p></jats:sec><jats:sec><jats:title>Patients and Methods</jats:title><jats:p> An international randomized, double-blind, placebo-controlled study was conducted in patients with completely resected IB to IIIA NSCLC whose tumors expressed EGFR protein by immunohistochemistry or EGFR amplification by fluorescence in situ hybridization. Patients were assigned 2:1 to erlotinib 150 mg once per day or placebo for 2 years. Stratification factors were stage, histology, previous adjuvant chemotherapy, smoking status, EGFR amplification status, and country. The primary end point was disease-free survival (DFS); key secondary end points were overall survival (OS) and DFS and OS in patients whose tumors had EGFR-activating mutations (EGFRm-positive). </jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p> A total of 973 patients were randomly assigned (November 26, 2007, to July 7, 2010). There was no statistically significant difference in DFS (median, 50.5 months for erlotinib and 48.2 months for placebo; hazard ratio, 0.90; 95% CI, 0.74 to 1.10; P = .324). Among the 161 patients (16.5%) in the EGFRm-positive subgroup, DFS favored erlotinib (median, 46.4 v 28.5 months; hazard ratio, 0.61; 95% CI, 0.38 to 0.98; P = .039), but this was not statistically significant because of the hierarchical testing procedure. OS data are immature. Rash and diarrhea were common adverse events occurring in 528 (86.4%) and 319 (52.2%) patients treated with erlotinib, respectively, versus 110 (32.1%) and 54 (15.7%) patients receiving placebo. The most common grade 3 adverse events in patients treated with erlotinib were rash (22.3%) and diarrhea (6.2%). </jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p> Adjuvant erlotinib did not prolong DFS in patients with EGFR-expressing NSCLC or in the EGFRm-positive subgroup. Further evaluation of erlotinib is warranted in the EGFRm-positive subgroup. </jats:p></jats:sec>