This study was undertaken in order to examine the roles of lipid peroxidation and poly (ADP-ribose) polymerase (PARP) activation in oxidant-induced renal cell death. Opossum kidney cell cultures were used as the renal epithelial cell model, and an inorganic hydroperoxide H 2 O 2 and an organic hydroperoxide t-butylhydroperoxide were employed as model oxidants. Cell death by both oxidants could be prevented by thiols (dithiothreitol and glutathione), iron chelators (deferoxamine and phenanthroline), and hydroxyl radical scavengers (dimethylthiourea and pyruvate). Phenolic antioxidants N,Nø-diphenyl-p-phenylenediamine (DPPD) and butylated hydroxyanisole had no effect on the H 2 O 2 -induced cell death . However, the t-butylhydroperoxide-induced cell death was effectively prevented by these antioxidants. The PARP inhibitor 3-aminobenzamide prevented the cell death induced by H 2 O 2 , but not cell death by t-butylhydroperoxide. The PARP activity was increased in cells exposed to H 2 O 2 but not t-butylhydroperoxide. Unlike in opossum kidney cells, in rabbit renal cortical slices both oxidants H 2 O 2 and t-butylhydroperoxide induced cell death through a lipid peroxidation-dependent and PARP-independent mechanism. Effects of DPPD and 3-aminobenzamide on H 2 O 2 -induced cell death in primary cultured rabbit proximal tubular cells were similar to those in opossum kidney cells. These results indicate that 1) the H 2 O 2 -induced cell death in cultured renal epithelial cells is associated with PARP activation but not lipid peroxidation, whereas the t-butylhydroperoxide-induced cell death is mediated by lipid peroxidation, and 2) the role of lipid peroxidation in H 2 O 2 cytotoxicity may be different between freshly isolated renal tubular cells and cultured renal epithelial cells.