Fas expression increases in perinecrotic areas of glioblastoma. In this study the up-regulation of Fas/FasL by oxidative stress was shown. H(2)O(2) exposure increased Fas expression in two astrocytoma cell lines and cells became sensitive to agonistic anti-Fas antibody. FasL was up-regulated in astrocytoma cells. Apoptosis of Molt-4 cells was augmented by astrocytoma cells pretreated with H(2)O(2). Our findings suggest up-regulation of Fas in astrocytoma cells may lead them to be sensitive to apoptosis when cells are in oxidative stress. Whereas, the up-regulation of FasL may render astrocytoma cells cytotoxic to neighboring brain tissues and infiltrating immune cells.