Hemoglobin is the predominent pigment in the gastrointestinal mucosa, and the development of electronic endoscopy has made it possible to quantitatively measure the mucosal hemoglobin volume, by using a hemoglobin index (IHb). The aims of this study were to make a software program to calculate the IHb and then to investigate whether the mucosal IHb determined from the electronic endoscopic data is a useful marker for evaluating the color of intramucosal gastric carcinoma with regard to its value for discriminating between the histologic types. We made a software program for calculating the IHb in the endoscopic images. By using this program, the mean values of the IHb for the carcinoma (IHb-C) and those of the IHb for the surrounding non-cancerous mucosa (IHb-N) were calculated in 75 intestinal-type and 34 diffuse-type intramucosal gastric carcinomas. We then analyzed the ratio of the IHb-C to the IHb-N (C/N ratio). The C/N ratio in the intestinal-type carcinoma group was higher than that in the diffuse-type carcinoma group (p<0.001). In the diffuse-type carcinoma group, the C/N ratio in the body was lower than that in the antrum (p=0.022). The accuracy rate, sensitivity, specificity, and the positive and negative predictive values for the differential diagnosis of the diffuse-type carcinoma from the intestinal-type carcinoma were 94.5%, 94.1%, 94.7%, 88.9% and 97.3%, respectively. IHb is useful for making quantitative measurement of the endoscopic color in the intramucosal gastric carcinoma, and the C/N ratio by using the IHb would be helpful for distinguishing the diffuse-type carcinoma from the intestinal-type carcinoma.