Changes in redox status of gastric mucosa cells are the main pathogenic factor of gastric erosion and gastric ulcer development. Pro-oxidants can affect cell transcription activity via changes in redox-sensitive transcription factors. Egr-1 and Sp-1 may regulate the transcription of genes that are associated with the pathogenesis of gastric ulcer (growth factors, cell cycle regulators, etc.). The aim of the present study was to reveal the possible involvement of zinc-finger transcription factors Egr-1 & Sp-1 in the molecular mechanisms underlying gastric lesions caused by aspirin administration and stress. Gastric ulcer was induced in male rats (180-220 g) by immobilization stress combined with water-immersion (IMO-WI) or aspirin gavage (10 mg/100 g). The rats were euthanized 20 min, 1 hour, or 3 hours following the ulcerogenic factor exposure. Protein expression was determined by Western blot analysis and RT-PCR; levels of SH-groups of proteins were determined by method of Ellman et al. Development of gastric ulcer lesions was associated with twofold (P < 0.05) decrease in concentration of protein SH-groups in the rat gastric mucosa. These changes were accompanied by significant (р < 0.05) increase in the expression of Egr-1 mRNA and protein in both gastric ulcer models, and the changes in IMO-WI were more profound. Increased levels of Egr-1 were associated with the decrease in Sp1 protein levels. We showed for the first time the competitive interaction between redoxsensitive transcription factors Egr-1 and Sp1 in the early phases of gastric ulcer development, which might facilitate inducible transcriptional activity of Egr-1 at the expense of reduction in Sp1 activity.