Low gastric juice total vitamin C concentration in the presence ofHelicobacter pyloriinfection probably plays a role in gastric carcinogenesis. Vitamin C plays a role in the neutralization of various pathogenic factors connected withH. pyloriinfection, including the destruction of free radicals, which damage tissues and cell DNA, and inhibition of the formation ofN-nitroso compounds, which have a strong carcinogenic activity. The aim of the study was to determine whether tobacco smoking had any effect on gastric juice vitamin C concentration in healthy subjects and in patients infected withH. pylori. Eighty-six patients with dyspeptic symptoms undergoing routine endoscopy entered the study after giving informed consent. In all patients plasma and gastric juice total vitamin C levels were measured by a spectrophotometric method. They were entered into four groups: group I (controls) –H. pylori-negative non-smokers (n = 17), group II –H. pylori-negative smokers (n = 16), group III – non-smokers withH. pyloriinfection (n = 21), and group IV –H. pylori-infected smokers (n = 32). In the control group (I) the mean gastric juice total vitamin C concentration was 17.1 μg/ml (range 5.3–40.0 μg/ml), which was significantly higher (P 0.05) than in group II (12.6 μg/ml, range 5.1–21.0 μg/ml), group III (5.8 μg/ml range 2.1–13.7 μg/ml) and group IV (3.9 μg/ml, range 1.1–10.6 μg/ml) (P 0.001). Statistically significant differences also were noted between groups II and III (P 0.01) and groups II and IV (P 0.001) and between groups III and IV (P 0.05). These results demonstrate that the concentration of vitamin C in gastric juice is significantly lower in smokers than in non-smokers. This was observed in healthy subjects as well asH. pylori-infected patients. This phenomenon may be one of the mechanisms whereby smoking contributes to the production of gastric lesions, impairs healing of peptic ulcers and also increases the recurrence rate of peptic ulcers in cases withH. pyloriinfection.