Background and aims: In the past decade of clinical studies, the combination of chemotherapy with cytokine induced killer (CIK) cell transfusion has confirmed a promised efficacy in several types of cancer. CIK cells are a mixture of T lymphocytes, generated from peripheral blood mononuclear cells induced by multiple cytokines. This study was aimed to evaluate the clinical efficacy of chemotherapy combined with CIK- cell therapy in patients with extensive stage small cell lung cancer (ES SCLC). Patients and Methods: Forty four patients with ES SCLC were enrolled in this study. All the patients received treatment from Oct 2010 to Sep 2013 in the First Affiliated Hospital of Zhengzhou University. Included patients were equally divided into 2 groups according to the treatment strategies. Patients in the combined treatment group received chemotherapy combined with CIK-cell transfusion and patients in the control group received chemotherapy alone. The short-term effects, overall survival (OS), progress free survival (PFS) and therapy-related adverse events were analyzed retrospectively. Results: Short-term efficacy evaluation indicated that the total response rates in the combined treatment group and control group were 40.9% (9/22) and 9.1% (2/22), respectively. There was a significant difference between the two groups (p = 0.0339). Furthermore, the PFS of the combined treatment group was significantly longer than that of the control group (8 vs. 4 months, P = 0.005). No severe side effect was observed after transfusion of CIK cells. Conclusion: These results indicated that chemotherapy combined with CIK-cell immunotherapy might provide a safe and effective treatment for patients with ES SCLC.