Objective To investigate the effect of methylguanidine and 1-methylhydantoin on cells cytotoxicity, apoptosis in human renal tubular epithelial cell line (HK-2). Methods Human PTEC cell line HK-2 was used in this study. HK-2 was cultured and divided into 3 groups: Norma1 control group (A), methylguanidine group(B) and 1-methylhydantoin group (C). The cell inhibitory rate of HK-2 was detected by MTT method. The cytotoxicity of methylguanidine to HK-2 was determined by NAG release test. Cell apoptosis was evaluated by using Hoechst stain and FACS with Annexin-V/PI. Results The OD value and NAG concentration of creatinine, methylguanidine and 1-methylhydantoin group were compared with normal control group. OD value decreased and NAG concentration significantly increased(0.188±0.011, 0.176±0.010 vs 0.545±0.021, F＝1557.74, P＜0.01; 20.488±0.473, 22.225±0.565 vs 5.125±0.198, F＝3848.22, P＜0.01). By Hoechst stain, pycnosis and apoptotic body could be found when HK-2 was cultivated in methylguanidine 1-methylhydantoin group. In methylguanidine, 1-methylhydantoin group apoptotic HK-2 apparently increased, compared with that in control group (18.23±1.1581, 20.22±1.1433 vs 2.473±0.321, F＝526.06, P＜0.01). Compared with group B, the OD value in group C decreased significantly (0.176±0.010 vs 0.188±0.011,t＝2.26, P＜0.05), NAG concentration increased significantly (22.225±0.565 vs 20.488±0.473,t＝-6.67, P＜0.01), and apoptotic rate in-creased significantly (20.22±1.1433 vs 18.23±1.1581,t＝-2.762, P＜0.05). Conclusions 1-methylhydantoin has more powerful cytotoxic effect to renal tubular epithelial cells than that of Methylguanidine.