We have investigated the effect of vitamin C (vit C) on malondialdehyde (MDA) and glutathione (GSH) levels in several tissues of rats treated with water-immersion restraint (WIR) stress. Hepatic and intestinal MDA levels increased significantly but GSH content remained unchanged after WIR stress. MDA levels declined following vit C supplementation. On the other hand, MDA and GSH levels were unchanged although ulcerogenic injury was seen in the stomach. Microscopically, this injury was reduced in the rats who received vit C. These results indicate that vit C may have a protective effect in stress-induced lipid peroxidation and gastric ulceration. Med Sci Res 26:595-597 (C) 1998 Lippincott Wiliiams & Wilkins.