目的　研究羟基喜树碱联合放射对人肺腺癌细胞的协同杀伤作用。方法　应用四唑盐比色试验 (MTT)检测细胞抑制百分比 ,DNA琼脂糖电泳检测DNA“Ladder”及流式细胞术检测细胞周期及凋亡峰的比例。结果　羟基喜树碱对该细胞的抑制呈剂量及时间依赖关系 ,且明显阻滞细胞于S期 ,低浓度的羟基喜树碱 (1μg/ml)作用 48小时 ,细胞开始出现凋亡小峰 ,高浓度的羟基喜树碱 (5 0 μg/ml)作用 2 4小时就出现明显的凋亡小峰。单纯放射 (6Gy)后 48小时细胞出现DNA“Ladder”条带 ,单纯羟基喜树碱 (1μg/ml)作用后 2 4～ 72小时 ,细胞出现DNA“Ladder”条带及凋亡小峰 ,细胞经羟基喜树碱联合放射作用后的 0～ 72小时均出现DNA“Ladder”条带及凋亡小峰。结论　羟基喜树碱联合放射对人肺腺癌细胞可能有协同杀伤作用 Objective To study the synergistic cytotoxic effect of hydroxycamptothecin combined with radiotherapy on human lung adenocarcinoma cells. Methods MTT assay was used to determine the percentage of cell cycle inhibition. DNA ladder assay was used to determine the ratio of cell cycle to apoptosis peak by flow cytometry. Results Hydroxycamptothecin inhibited the cells in a time-and dose-dependent manner, and blocked cells in the S phase, low concentrations of hydroxycamptothecin (1μg / ml) for 48 hours, cells began to witness a small peak, high Concentration of hydroxycamptothecin (50 μg / ml) effect 2 4 hours obvious apoptotic peak. DNA “Ladder” bands appeared at 48 hours after radiotherapy (6 Gy), and DNA “Ladder” bands and small apoptotic peaks appeared after 24 h to 72 h after treatment with hydroxycamptothecin (1 μg / ml) DNA “Ladder” bands and small apoptotic peak appeared between 0 and 72 hours after hydroxycamptothecin combined with radiotherapy. Conclusion Hydroxycamptothecin combined with radiotherapy may have a synergistic cytotoxic effect on human lung adenocarcinoma cells