The objectives of the present study using cultured mouse mesangial cells (MMC) were (1) to evaluate the type of cytotoxicity induced by oxidized (ox) LDL, i.e. apoptosis, necrosis and types of other cell death and (2) to investigate the pathway of cell death under incubation with antioxidants or scavenger receptor (SR) antagonists. LDH release and a morphological examination were used in this study. Trypan blue staining of MMC was performed to detect dead cells in culture. Cytotoxicity of ox-LDL in MMC was found to be dose- and time-dependent. In the morphological study of electron microscopy, three different types of cell death in ox-LDL-treated MMC were identified. In the morphological study with semithin sections, these three types of dead cells were identified at different dosages of ox-LDL. Type 1 or type 2 dead cells were observed in low dose ox-LDL or in middle-dose ox-LDL-treated MMC, respectively. Type 3 dead cells were marked in high dose ox-LDL-treated MMC. It appears that the cells were apoptotic (type 1), necrotic (type 3) and other types (type 2). The cytotoxicity of ox-LDL was not mediated by cellular internalization of ox-LDL via SRs. On the other hand, the cytotoxicity of ox-LDL was inhibited by antioxidants such as α-tocopherol, probucol, N-acetyl-cysteine or glutathione ethyl ester. It is indicated that the pathways of ox-LDL induced cell death were distinct from the pathway via SRs.