Background: Statistically high prevalence of malignant neoplasm of digestive organs in the city of Łódź encouraged us to make an attempt to evaluate effects of adverse environmental factors and Helicobacter pyroli infection on the selectedparameters of oxygen metabolism. Materials and Methods: The study group consisted of 50 Łódź inhabitants, living and working in the center of the city, exposed to carcinogenic environmental factors. Of this number, 25 subjects were infected with Helicobacter pyroli and 25 subjects were free from the infection. The control group comprised 50 nonexposed persons living in the Łódź voivodship. The control group was also divided into two sub-groups: 25 persons with and 25 persons without Helicobacter pyroli infection. In each subject, blood serum superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, as well as malonic dialdehyde (MDA) concentration and total plasma antioxidative activity (TAA) were determined. Results: In the group of subjects exposed to carcinogenic environmental factors and also infected with Helicobacter pyroli, activity of SOD, GPx and TAA was lower than in the infected subjects without risk of exposure to adverse environmental factors, but MDA concentrations were found to be higher. The values of the parameters studied did not differ significantly among the Łódź inhabitants without Helicobacter pyroli compared to infected subjects. However, in inhabitants of the Łódź voivodship without Helicobacter pyroli infection, the differences were statistically significant in comparison with the infected group. Conclusions: The examinations revealed significant disorders of the oxidation-antioxidation system in subjects exposed to carcinogenic environmental factors. An additional factor, i.e., Helicobacter pyroli infection, which potentially impair oxygen metabolism, did not exert significant effect on the inhabitants of Łódź.