OBJECTIVE To conduct a systematic review and to evaluate the impact of postoperative adjuvant chemotherapy on the survival of patients with completely resected non-small cell lung cancer. METHODS Relevant randomized trials and meta-analyses, published as articles or abstracts, were identified through electronic and hand searches by two reviewers. RESULTS Seven meta-analyses and 26 randomized trials comparing surgery with or without chemotherapy met the pre-defined eligibility criteria for the review. The meta-analyses all showed a survival advantage for platinum- or UFT-based postoperative chemotherapy, although the results did not always achieve statistical significance. The results of individual trials were inconsistent, although recent trials have detected a large survival advantage with postoperative platinum-based chemotherapy. Differences in trial design, patient characteristics, disease stage, use of radiotherapy and chemotherapy regimen may explain the variation in results. CONCLUSIONS Postoperative adjuvant platinum-based chemotherapy improves survival compared with surgery alone in completely resected non-small cell lung cancer. In patients fit for chemotherapy, the survival benefits strongly outweigh the adverse effects of the treatment.