To investigate the pathology of gastric disorders, we compared the proteomic patterns of gastric juice from patients with various gastric disorders. In healthy subjects pepsin A, pepsin B and gastric lipase were the major proteins detected by two-dimensional gel electrophoresis. These digestive enzymes were not detected in 60% of gastric cancer cases (18 out of 30 analyzed cases). Interestingly, an extraordinary amount of α1-antitrypsin was observed in these cases. In contrast to gastric cancer cases, α1-antitrypsin was detected in only 5% of patients (three out of 56) with chronic atrophic gastritis, and the detection frequency went up as the disease developed (one of four intestinal metaplasia cases, two of seven tubular adenoma cases, a single examined case of hyperplastic polyp and 60% of gastric cancer). Zymography showed that a 60 kDa protease strongly associated with α1-antitrypsin and mass spectrometric analysis revealed that the gastric α1-antitrypsin was a protease-cleaved form. Our data suggest that α1-antitrypsin and 60 kDa protease may serve as good diagnostic and prognostic markers for conditions associated with gastric cancer.