Sixty-eight patients (45 males, 23 females) were studied in order to assess the usefulness of mucosal tissue concentrations of both carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) in detecting patients at high risk for gastric cancer. CEA and CA19-9 were assayed on cytosol obtained from multiple endoscopic biopsies of 41 patients with chronic superficial gastritis, 18 with chronic atrophic gastritis, and 9 with gastric cancer. Mucosal tissue concentrations of both CEA and CA19-9 increased from chronic superficial gastritis to chronic atrophic gastritis and to gastric cancer (p = 0.005 and p = 0.002, respectively). Mucosal CEA levels in patients with intestinal metaplasia (IM) were significantly higher than in nonmetaplastic mucosa (p = 0.04). Epithelial dysplasia was associated with higher, though not significant, tissue concentrations of both CEA and CA19-9 when compared with IM. Finally, a correlation between serum levels and tissue concentrations was observed only for CA19-9 (Pearson's correlation coefficient = 0.7). In conclusion, these data indicate that gastric mucosa of patients with chronic atrophic gastritis and intestinal metaplasia express high levels of both CA19-9 and CEA.