目的　研究褪黑激素对体外培养的人宫颈癌 (HeLa)细胞活性的影响。方法　MTT测定褪黑激素的抗肿瘤活性 ;电镜观察药物对肿瘤细胞形态学的影响 ;流式细胞仪检测药物对肿瘤细胞周期的影响。结果　高浓度 (2mmol·L- 1 )褪黑激素可抑制HeLa细胞的生长 ,使细胞倍增时间TD 延长 ,细胞杀伤率达 6 1 0 %。用此浓度作用 3天 ,可使S期细胞的比例减少 ,细胞形态学发生非特异性改变 ,有较多的坏死细胞和少量凋亡细胞。结论　高浓度褪黑激素抑制HeLa细胞增殖 ,可能与抑制细胞的S期有关 Objective To investigate the effect of melatonin on the activity of human cervical carcinoma (HeLa) cells cultured in vitro. Methods The antitumor activity of melatonin was determined by MTT. The morphological changes of tumor cells were observed by electron microscopy. The effect of drugs on the cell cycle was detected by flow cytometry. Results High concentration (2 mmol·L -1) of melatonin could inhibit the growth of HeLa cells and prolong the cell doubling time TD with a cell killing rate of 610%. With this concentration for 3 days, can reduce the proportion of S-phase cells, nonspecific changes in cell morphology, there are more necrotic cells and a small number of apoptotic cells. Conclusion High concentration of melatonin can inhibit the proliferation of HeLa cells, which may be related to the inhibition of S phase