Antioxidants such as glutathione, N-(2-mercaptopropionyl)glycine (MPG), vitamin E, vitamin C and a combination of vitamin E and vitamin C in different treatment schedules were evaluated for their antiemetic activity against cisplatin-induced emesis in dogs. While cisplatin-induced emesis was significantly reduced by all these agents, glutathione, MPG and combination of vitamin E and vitamin C produced maximum reduction. The antiemetic activity of antioxidants may be attributable to their ability to react with free radicals generated by cisplatin. The present study provides further evidence that free radicals play a role in cancer chemotherapy induced emesis and warrant clinical evaluation.