A systematic review of radiation therapy trials in several tumour types was performed by The Swedish Council of Technology Assessment in Health Care (SBU). The procedures for evaluation of the scientific literature are described separately (Acta Oncol 2003; 42: 357-365). This synthesis of the literature on radiation therapy for non-small cell lung cancer (NSCLC) is based on data from 4 meta-analyses and 31 randomized trials. Moreover, data from 12 prospective studies, 12 retrospective studies and 6 other articles were used. In total, 65 scientific articles are included, involving 18 310 patients. The results were compared with those of a similar overview from 1996 including 28 172 patients. The conclusions reached can be summarized as follows: Extensive clinical experience indicates that radiotherapy for medically inoperable patients or patients refusing surgery with NSCLC stage I/II prolongs survival, 15 -20% of these patients reaching long-term (5-year) survival. However, no randomized trials have addressed this issue. There is strong evidence that postoperative radiotherapy in radically resected stage I/II NSCLC does not prolong survival compared with observation alone. There is some evidence that continuous hyperfractionated accelerated radiotherapy (CHART) is associated with increased survival compared to conventional radiotherapy in locally advanced NSCLC and also in medically unfit patients with stage I/II NSCLC. However, the benefit is limited to squamous cell histology. There is strong evidence that combined modality treatment with platinum-based chemotherapy and radiotherapy, either neoadjuvant or concomitant, is superior to radiotherapy alone in terms of survival in locally advanced unresectable NSCLC and should be the standard of care in patients with good performance status. There is some evidence that concomitant chemo-radiotherapy is associated with increased survival compared with sequential chemo-radiotherapy, albeit at the price of increased toxicity Comment: Combined chemo-radiotherapy of primary non-resectable stage III NSCLC followed by surgery in responders lacks evidence from prospective randomized trials and cannot be recommended for routine use. There is strong evidence that radiotherapy can palliate symptoms associated with the intrathoracic tumour burden. There is some evidence that two large fractions may be as effective as conventional schedules consisting of 10-13 smaller fractions in terms of palliation of symptoms. There is some evidence that endobronchial brachytherapy for palliation of symptoms associated with endobronchial tumours is not superior to external beam radiotherapy.