Abstract： Objective The function of induced apoptosis of tumorinfiltrating lymphocytes (TIL) to lung carcinoma cell line (A549) was studied in this paper.The basic data of study was provided for the clinical application of TIL's treatment to lung carcinoma.Methods The TIL cells were separated from pleural effusion of lung carcinoma patients by Ficoll-Hypaque (1.077±0.001) After cultured for 20 days in completed medium with 1000U/ml IL-2, TIL cells co-cultured with target cells (carcinoma cell line) for 24 hours. Then cultured cells were smeared on the slides, and fixed the slides in 10% formalin.Apoptotic carcinoma cells were labeled by TdT-mediate dUTP nick end labeling(TUNEL) method.Results Apoptotic index (%)of carcinoma cells was:8.56±0.84 in TIL experimental group, 2.10±0.86 in control group.There was different significance between the above two groups(p<0.01).Conclusions Apoptosis of lung carcinoma cells induced by TIL cells may be one of the mechanisms of TIL cells killed lung carcinoma cells.