A growing body of evidence suggests that postoperative irradiation for non-small cell lung cancer may cause life-threatening toxicity and, when the risk of local-regional recurrence is low, the toxicity of irradiation may outweight the benefit. However, many of these studies used outdated, even crude techniques. Although these techniques may be responsible for a significant amount of the toxicity reported in these studies, essentially no randomized or high-quality retrospective study has shown a survival benefit for postoperative irradiation for patients with N0 or N1 disease. The situation for N2 tumors is more positive. Taken as a whole, the available data suggest that, as a worst-case scenario, the net effect of adjuvant irradiation is neutral (with neither a net survival decrement nor a net advantage). As a best-case scenario, postoperative irradiation may improve the chance for long-term survival in patients with N2 tumors. Copyright (C) 2000 by W.B. Saunders Company.