Background: It has been suggested that the variation of biochemical and microbiological parameters in the gastric juice may play a role in the development of gastric cancer. In the present study we concurrently assessed the presence of N-Nitroso compounds (NOC) and their precursors, bacteria and carcinoembryonic antigen (CEA) in the gastric juice of normal controls, patients with gastric resection, and advanced gastric cancer., Methods: Detailed analyses of biochemical and microbiological parameters such as pH, nitrite (NO2) concentration, N-nitroso compounds (NOC) concentration, carcino-embryonic antigen (CEA) level, total viable counts (TVC), nitrate-reductase positive bacterial counts (NRPBC), and identification of micro-organisms were carried out., Results: Significantly higher mean pH values, NO2, NOC and CEA concentrations, TVC, and NRPBC were found in partial gastrectomies compared with normal controls, and all these intragastric parameters were significantly higher in patients with gastric cancer than in those with partial gastrectomies. As far as surgical methods are concerned, higher mean pH values, NO2 and NOC concentrations, TVC, NRPBC, and anaerobic bacterial counts were observed in the juice of patients with Billroth II compared with Billroth I gastrectomies. Apart from the type of surgical reconstruction, higher mean NOC levels were recorded in patients with more severe histological changes and H. pylori infection., Conclusions: All these data suggest that the presence of high levels of NOC in the gastric juice of gastroresected patients can be considered a risk factor of gastric stump cancer.