Combined modality treatment of patients with stage III non small-cell lung cancer (NSCLC) has recently become widely accepted. Standard combinations are neoadjuvant chemotherapy followed by radiotherapy or concurrent chemotherapy and radiotherapy. The effect of combined modality treatment on survival is dependent on both the efficacy of chemotherapy to eradicate micrometastases and optimal local control. The European Organization for Research and Treatment of Cancer (EORTC) Lung Cancer Cooperative Group has chosen to investigate in a comparative way the side effects and the effect on survival of radiotherapy versus surgery in stage IIIA (N2) NSCLC.