Hansenula mrakii IFO 0895 induces glutathione peroxidase as an oxidative stress response. Activities of other antioxidant enzymes-superoxide dismutase, catalase and cytochrome c peroxidase-were assayed. The superoxide dismutase activity did not change when the cells were cultured in the presence of lipid hydroperoxide, whereas the catalase and cytochrome c peroxidase activities decreased. The intracellular glutathione content and the activities of enzymes involved in glutathione biosynthesis were not changed by oxidative stress. Glucose-6-phosphate dehydrogenase, which is involved in the glutathione recycling system, was induced by oxidative stress to supply NADPH which is consumed by glutathione reductase coupling with the glutathione peroxidase reaction.