Objective To evaluate the efficacy of concurrent radiotherapy combined with carboplatin and etoposide in treatment of small cell lung cancer at localized stage(LS-SCLC).Methods From January 1998 to December 2000,46 patients with small cell lung cancer at localized stage were randomized into two groups: concurrent treatment group (group A) and sequential treatment group(group B). All the patients in two groups received conventional radiotherapy (~60 Gy in 6 weeks) and four courses of chemotherapy (carboplatin and etoposide). Radiotherapy was started in the first course of chemotherapy in group A.Patients of group B were treated with radiation after the fourth cycle of chemotherapy.Results The median survival time was 30 months in group A and 20 months in group B. The 5-year survival rate was 27% in group A and 16% in group B. The major toxic reaction was grade Ⅲ-Ⅳ myelosuppression.The differences between the two groups were significant (P0.05).Conclusion Concurrent radiotherapy combined with carboplatin and etoposide can significantly improve survival rate of patients with small cell lung cancer at localized stage.Chemotherapy plus approximately 60 Gy of once-daily radiotherapy for LS-SCLC is tolerable.