A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was whether patients benefit in terms of survival from chemotherapy following complete resection of non-small-cell lung cancer. Altogether 681 papers were found using the reported search, of which 14 represented the best evidence on this topic. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. We conclude that post-operative adjuvant chemotherapy carries a small survival benefit in those patients with complete resection of their lung cancer. This survival benefit is in the region of a 4% absolute survival advantage at 5 years. Thus, 25 patients require chemotherapy to save one life at 5 years. This should be discussed with all the patients following complete resection of non-small-cell lung cancer.