For many years, surgery alone was the standard treatment for patients with stage I-IIIA non-small-cell lung cancer (NSCLC). However, recent studies have demonstrated that adjuvant chemotherapy provides a survival benefit. The first adjuvant chemotherapy for NSCLC was performed in the 1960s using a key drug known as cyclophosphamide. In the 1980s and early 1990s, a new anti-cancer drug, cisplatin, was developed. The first meta-analysis of this drug was conducted by the Non-small Cell Lung Cancer Collaborative Group in 1995. This analysis comparing surgery with surgery plus chemotherapy containing cisplatin produced a hazard ratio of 0.87 and suggested an absolute benefit of chemotherapy of 5% at 5 years;this difference was not statistically significant (p0.08). Several clinical trials of adjuvant chemotherapy were planned after the meta-analysis conducted in 1995, but the efficacy of adjuvant chemotherapy remained a matter of controversy. However, useful evidence was reported after 2003. The International Adjuvant Lung Cancer Collaborative Group Trial (IALT) demonstrated a 4.1% improvement in survival for patients with stage I to III NSCLC. The JBR. 10 trial demonstrated a 15% improvement in 5-year survival for the adjuvant chemotherapy arm in stage IB or II (excluding T3N0) patients. The Adjuvant Navelbine International Trialist Association (ANITA) trial reported that the overall survival at 5 years improved by 8.6% in the chemotherapy arm and that this survival rate was maintained at 7 years (8.4%) in stage II and IIIA patients. A meta-analysis based on collected and pooled individual patient data from the 5 largest randomized trials was conducted by the Lung Adjuvant Cisplatin Evaluation (LACE). This analysis demonstrated that cisplatin-based adjuvant chemotherapy improved survival in patients with stage II or III cancer. Alterna-tively, uracil-tegafur has been developed and tested in Japan. The Japan Lung Cancer Research Group (JLCRG) on Postsurgical Adjuvant Chemotherapy reported a 5-year overall survival advantage of 11% in the uracil-tegafur group patients with stage IB cancer. The efficacy of adjuvant chemotherapy with uracil-tegafur was confirmed in a meta-analysis. In conclusion, the results of phase III trials and a meta-analysis have confirmed the benefit of adjuvant chemotherapy for resected stage IB, II, and IIIA NSCLC.