Serum superoxide dismutase, plasma ascorbic acid and lipid peroxidation in H. pylori gastritis and gastric cancer patients were compared with values for age matched healthy subjects. Serum superoxide dismutase and serum malondialdehyde were analyzed spectrophotometrically whereas plasma ascorbic acid was determined by colorimetric method. Significant increase in serum superoxide dismutase and serum malondialdehyde and significant decrease in plasma ascorbic acid were observed in H. pylori gastritis and gastric cancer patients compared to control subjects. The concentration of serum superoxide dismutase and serum malondialdehyde was significantly higher and plasma ascorbic acid was significantly lower in gastric cancer as compared to H. pylori gastritis patients. Our results demonstrate that a correlation existed between the concentration of serum superoxide dismutase, plasma ascorbic acid and lipid peroxidation in H. pylori gastritis and gastric cancer patients.