Overexpression of cyclooxygenase-2 (COX-2) is frequently present in lung cancer and may play a significant role in carcinogenesis, invasion, and metastasis. It has been associated with shortened survival in patients with resected early-stage adenocarcinoma of the lung. COX-2 inhibition decreases tumor cell proliferation in vivo and has been shown to enhance tumor radiosensitivity. Additionally, COX-2 inhibition may protect normal pulmonary tissue from radiation fibrosis. Clinical studies are under way to assess the potential benefits and risks of COX-2 inhibition in the treatment of lung cancer. The rationale for COX-2 inhibitors in the treatment of lung cancer will be reviewed. The results of a phase II study assessing the acute toxicity of concurrent celecoxib (Celebrex) and thoracic irradiation in patients with non-small-cell lung cancer (NSCLC) are reported, and an ongoing Radiation Therapy Oncology Group study using celecoxib and concurrent radiation therapy for NSCLC in patients with intermediate prognostic factors is reviewed.