Abstract: To investigate the effect and mechanism of cytotoxicity by rhein in human renal tubular epithelial HK-2 cells, HgCl₂ was choosen as positive control. Cell viability was determined by MTT assay. LDH release assay was used to evaluate cell membrane damage. The activity of caspase-3, and -8 was measured by assay kit. Real-Time qPCR was employed to determine the mRNA expressions of Fas, FasL, FADD, caspase-3 and caspase-8. The protein expressions of Fas, FasL, cytoplasmic cytochrome C, caspase-3, caspase-8, caspase-9 were detected by Western blot. The results demonstrated that rhein inhibited cell viability and increased LDH release in a dose-dependent manner. The activity of caspase-3 and caspase-8 was significantly enhanced by rhein. The mRNA expression of Fas, FasL, FADD, caspase-3, caspase-8 was remarkably up-regulated by rhein. Rhein also elevated protein expressions of Fas, FasL, cytoplasmic cytochrome C, cleaved caspase-3, caspase-8 and reduced expressios of Pro caspase-8. There was no significant difference in caspase-9 expression. These results indicate that rhein has a cytotoxic effect and apoptosis-inducing effect in HK-2 cells. The Fas-dependent pathway is involved in rhein-induced apoptosis.