BACKGROUND: Chemotherapy combined with surgical resection improves survival in patients with stage II to IIIA non-small cell lung cancer (NSCLC) and may benefit selected patients with stage IB disease. We sought to evaluate chemotherapy use in resected stage IB to IIIA NSCLC over time and to identify predictors of perioperative chemotherapy administration. METHODS: Patients with resected stage IB to IIIA NSCLC were identified from the National Cancer Data Base (2002 to 2011). Administration of chemotherapy was assessed over time. Hierarchical regression models were developed to assess patient, hospital, and tumor-level characteristics predicting perioperative chemotherapy administration. RESULTS: In 55,016 stage IB patients, chemotherapy use significantly increased between 2002 and 2011 from 5.3% to 15.1% (p < 0.001). In 57,033 patients with stage II to IIIA disease, perioperative chemotherapy administration also significantly increased from 29.3% to 58.4% (p < 0.001). Multivariable analyses demonstrated stage IB and II to IIIA patients were less likely to receive chemotherapy if they were older, treated at an academic center (vs community), had more comorbidities, or had lower-grade tumors (all p < 0.05). Stage IB patients with tumors sized 4 cm or larger were more likely to receive chemotherapy (odds ratio, 3.16; 95% confidence interval, 2.73 to 3.65) than those with tumors smaller than 4 cm. Compared with stage IIA patients, stage IIB patients were no more likely to receive perioperative chemotherapy (odds ratio, 1.06; 95% confidence interval, 0.96 to 1.17), whereas stage IIIA patients received chemotherapy significantly more often (odds ratio, 2.82; 95% confidence interval, 2.55 to 3.11). CONCLUSIONS: The use of chemotherapy has significantly increased in patients with resected stage IB to IIIA NSCLC. Although clinicians have increasingly adopted evidence-based recommendations, significant treatment gaps persist and represent areas for quality improvement.