Objective To investigate the expression of IL-24 in patients with non-small cell lung cancer (NSCLC),and to evaluate its influence on the bioactivity of NSCLC cells. Methods Thirty-nine patient with NSCLC (23 patients with adenocarcinoma and 16 patients with squamous carcinoma) and 17 healthy subjects were enrolled in this study. Serum samples and lung cancer tissues were collected. IL-24 expression in the serum samples was measured using enzyme-linked immunosorbent assay. Its expression at mRNA level in the lung cancer tissues was measured using reverse transcriptional real-time PCR. Adenocar-cinoma cell line A549 and squamous carcinoma cell line NCI-H520 were stimulated with recombinant human IL-24 (10 ng/ml and 100 ng/ml) for 24 hours. Cell proliferation was measured using CCK-8 method. Ap-optosis and cell cycle were measured using flow cytometry. Cell invasion was measured using Transwell as-say. Results Serum IL-24 was significantly elevated in patients with NSCLC in comparison with that in healthy subjects [(144.10±64.43) vs(48.47±18.00) pg/ml]. No significant difference in IL-24 expres-sion was found between patients with adenocarcinoma and squamous carcinoma. IL-24 expression at mRNA level in lung cancer tissues of patients with NSCLC was also significantly increased with an approximately 5-fold enhancement in comparison with that in normal lung tissues. Stimulation with low concentration of re-combinant IL-24(10 ng/ml) promoted the proliferation and suppressed the apoptosis of A549 and NCI-H520 cells. In contrast, high concentration of recombinant IL-24 (100 ng/ml) stimulation notably inhibited the proliferation and enhanced the apoptosis of lung cancer cell lines. No remarkable changes in cell cycle of the two kinds of lung cancer cells in response to IL-24 stimulation were observed. Moreover,low concentration of recombinant IL-24 (10 ng/ml) did not affect the invasion of A549 and NCI-H520 cells,while high concen-tration of recombinant IL-24 (100 ng/ml) significantly inhibited the invasion of lung cancer cells. Conclu-sion IL-24 might influence the bioactivity of NSCLC cells in a concentration-dependent manner. High con-centration of IL-24 might counteract the invasion and metastasis of NSCLC,which is important to prevent dis-ease promotion.