The aim of this study was to establish a computer-aided estimating system for determining the risk of development of gastric cancer, achieved by image processing on an ordinary endoscopic picture. Digital endoscopic pictures of the background gastric mucosa in 26 Helicobacter pylori (H. pylori) positive patients with early intestinal type gastric cancer and age-gender-matched H. pylori positive subjects without cancer were used. The pictures were processed for 15 pictorial parameters. Out of the 15 pictorial parameters, 3 parameters were found to characterize the background gastric mucosa with gastric cancer against that without. Based on the Bayes decision theory, the computer-aided estimating system has been established. Sensitivity, specificity, positive predictive value and negative predictive value of the Bayes classifier were found to be 0.64, 0.64, 0.65 and 0.63, respectively. This method may permit an effective selection of the high risk population of gastric cancer needing follow-up endoscopy.