Lung cancer is the leading cause of cancer-related death among men and women in the world. Despite the aggressive treatment with surgery, radiation and chemotherapy, the long term survival for lung cancer patients remains low. In this study, the anti-tumor activity of cytokine-induced killer (CIK) cells against human lung cancer was evaluated in vitro and in vivo. Although CD3(+)CD56(+) CIK cells were rare in fresh human peripheral blood mononuclear cells, they could expand more than 1000-fold on day 14 in the presence of anti-CD3 antibody plus IL-2. At an effector-target cell ratio of 30:1, CIK cells destroyed 98% of NCI-H460 human lung cancer cells, which was determined by the (51)Cr-release assay. In addition, CIK cells at doses of 3 and 30 million cells per mouse inhibited 57% and 77% of NCI-H460 tumor growth in nude mouse xenograft assay, respectively. This study suggests that CD3(+)CD56(+) CIK cells may be used as an adoptive immunotherapy for patients with lung cancer.