Our main purpose was to determine whether the addition of thoracic radiation therapy to systemic chemotherapy improves 2-year survival, improves local (intrathoracic) tumor control, and affects treatment-related mortality in patients with limited-stage small-cell carcinoma of the lung. Eleven randomized trials addressing this issue were identified using a computerized literature search (Medline and Cancerline) and by polling senior investigators in the field. A meta-analysis was then performed and the results of the trials were analyzed in two ways, the odds ratio (OR) (Peto) method and the risk difference method (Dersimonian and Laird). The overall OR for benefit of thoracic radiation on 2-year survival (ie, the odds of surviving 2 years among patients allocated to radiation compared with the odds of surviving 2 years among patients allocated to control) is 1.53 (95% confidence interval [CI], 1.30 to 1.76; chi 2 = 12.76; P less than .001). The risk difference method showed that radiation therapy improved 2-year survival by 5.4% (95% CI, 1.1% to 9.7%). Local control results were available for only nine studies, the OR for treatment benefit is 3.02 (95% CI, 2.80 to 3.24; chi 2 = 101.48; P less than .0001), and intrathoracic tumor control was improved by 25.3% (95% CI, 16.5% to 34.1%). The OR for excess treatment-related deaths in the thoracic radiation-treated patients was 2.54 (95% CI, 1.90 to 3.18; chi 2 = 8.24; P less than .01). The risk difference for treatment-related deaths was 1.2% (95% CI, -0.6% to 3.0%). This meta-analysis shows a small but significant improvement in survival and a major improvement in tumor control in the thorax in patients receiving thoracic radiation therapy. However, this is achieved at the cost of a small increase in treatment-related mortality.